Okay, so I've heard everyone say how wonderful these NGK TR55 plugs were.

I've also heard folks say that the plugs / wires don't matter, for performance..

So off to test I was. I pulled my two month old Bosch+4 Platinums and installed the NGK'* without any other mods.

What I found was a car that ran "normal" and smooth, but didn't have anywhere near the power as it did before. Also the sound from the exhaust was different. Quieter.

I ran these guys for a few days while running around town. No "problems" but not the SSE I was used to. It was like being in a boring normal car. Not my SSE. There was a noticeable drop in take off power and in acceleration.

We've watched videos posted here and even my son commented on the fact that there seemed to be some points in the acceleration where things leveled off. We'd watch the speedometer clime then slow down in the 90-100 range and then clime to 100-110 etc.

That'* what we saw with these plugs. It would still do the top speed, but didn't have the power it used to and would take a long time to get there. Outside Temps ranged between 30s to 70s during the tests.

So after a couple of days having a "crippled" car, compared to what it was, I wanted to make sure that there wasn't something wrong with it. I also wanted my power back.

So I put back the Bosch+4s, replacing #4 with a new one as it had broken during removal. Back out on the road. Power was back! Exhaust sound was back! All of it was back. Outside temp was 66-70F and it ran great.

I ran the top speed test again, and everything worked out great. Same full speed climb I used to have. Driving on a level surface kept us planted in our seats all the way to max. (Stock PCM). Another thing my son noticed was that the power was still there at 100+. I'd let my food off for a sec, then plant it again and you could feel the acceleration.. Up to the limit..

This was a totally different experience than with the NGKs.

I'll have some pics to post later. Plug tips, etc. With all deference to other'* experience, this worked for me. This may not be the proper plug for a SC vehicle, but for my NA SSE, they rock!

Keep in mind I pulled the Bosch, put in the NGKs, drove for a few days but never had the sound or power that the other plugs gave me and when I replaced the Bosch, it all came back. That'* more than enough proof that they work for me.

The only thing that'* not "stock" other than the plugs is a K&N replacement filter (not the cone ones, the square that goes in the stock intake box).

I did try what others said was the "best", and I may get a lot of grief here over it not working the way the regulars here said it would. But, I did the most fair test I could think of and it came out for the plugs I was already using.

Last night my son and I put in new rear struts (Monroe #71798 Sensatrac) and outer rear tie rod ends (Moog #ES2500RL). The struts were way past due for changing, and made a huge difference. The tie rod ends were original and the rubber boots were crumbling. so since I had to get the alignment anyway, I put them on now. Hopefully the rear is done for a while.

Also, this morning I changed the plugs wires to Splitfire Dual Core 8MMs, also minor improvements in sound and power. Not as dramatic as the plugs were, but some noticeable power. We'll see over the long term. I've got some pics of that too.

It'* in the 60s and 70s here, so I had to do all this stuff this week.

Okay, here are some pics of the +4s w/ two months on them:


All Plugs in order from bottom up: 246 on left and 135 on right


Angled view of one plug'* tip.


Top view of one plug'* tip.


Angled view of the new plug for #4.

I have 5 slightly used NGK55s if someone wants them very badly... Actually Advanced said that they'd take them back. They only recommend them for SC engines.

I doubt you'll get any grief.

What many have found is that the platinum plugs are not for the SC engines. The copper plugs will produce a spark better under a boost condition.

Now..on the NA application like yours, the plugs are working well for you. Overall, it is my understanding the club as a whole has seen lesser mileage on the platinums than would be expected. I would have liked to see a comparison to the Iridiums vs the Plats. Say a Delco Iridium vs your plats.

I happen to have a set of Irids at home w/about 3K miles on them...interested in giving them a try and see if the power/sound changes?

Well I can definitely say that I noticed the same exact thing you did when I went from Bosch +4s to TR55s... But remember, the bosch may be good now, but apparently they don't last a very long time. I personally have had alot better luck with Bosch products than most people here. But most these guys know their stuff really well. I trust NGK more for their longevity. But I would say maybe you should check out NGK'* full line of plugs! They have quite a few. TR55s are just the base plug, they have some amazing laser iridium $10/ea plugs which are supposed to be pretty good. But if you really like those +4s, which I do personally agree with that they make the car run with a little more kick, go ahead and keep them, but only if you feel like replacing them when they go bad @ the price those things are at.

*this is all just an opinion from personal experience*

Technically.. the NGK TR55 isn't an equal to the plats, the iridiums are supposed to be equal or better.

I actually had Denso Iridiums on there before switching to the +4s. After the UIM/LIM leak I had to put in new plugs and they were out of the Densos. But I was very happy with the Bosch plugs when I put them in. the seemed better than the other ones, but with the coolant problems, that would be expected..

The thing that wasn't expected is that the plugs seem to be using all four grounds electrodes. If you look at the pics, you can see that all four have the same pattern from the center for the sparks. I was glad to see that.

If someone wants to donate plugs for my next test, I'm all for that. Maybe I can record sounds too. But it will have to be a warm spell for me to change them out again.

I'd prefer the New Bosch Fusion Iridium/Platinum for the next test, but hey. I'll try anything except stock copper plugs. It just seemed a waste of time and I missed my car'* power too much.

One other thing, my car is 10/11 years old, but it has less than 90K on it. I don't know if that makes a difference or not.

Yes..the purpose of those four grounds is to be used. Same principle as the Splitfire plugs.. more grounds...to give the spark more places to jump.

Chip, can you put your year and model in your signature by editing your profile?

And you did struts and tie-rod ends? How about those swaybar endlinks? Most of us notice a HUGE difference from changing those.

I didn't know about those endlinks. Where should I get the new / performance ones from?

Are you talking about one of these kits (Moog From Rock Auto)?


Also, how'* the sig now? Maybe I need a pic too.

Get the Energy Suspension kits from Autozone. The front is a simple measurement. The back you'll need new GM bolts, or generic bolts that do NOT have threads where the bushings will rest, and buy the universal bushing/washer kit.

Try a search here. You'll find all you need to know.