Just got a ZZP 3" Dowpipe and 3" high flow cat installed.
 

Costed me $290.00, including installation.

The car feels somewhat more responsive at WOT and has a somewhat raspier/louder tone too it when you punch it.

This mod packs more punch then my first mod which was an off the shelf PCM tune.

They say ZZP's downpipe and cat is supposed to trigger a SES light on 2000+ SSEI's but i do not have one as of right now.

Overall im pleased with this mod, and im curious on what you guys think should be my next mod??

If you can swing the price, headers. If not, then a front Plog, make sure you get the stainless steel one, the mild steel tend to crack a lot.

I probably wouldn't have suggested the downpipe as the W body and H body differ for the main restriction point.

However the power log is a good addition to your fairly free flowing exhaust. There's a down side to it in that many of them crack and have issues.

After a power log and intake you will want a real tune, not the off the shelf 1.0 and probably a 3.5 or 3.4 pulley.

As an aside I was reading another forum this morning where 5-6 members have blow engines running lean with some exhaust work and a ZZP 1.0 pcm. I'd suggest scanning fuel trims etc to ensure if you are or aren't running lean before enjoying your new found power. Lean is fast and lean is bad for the motor. Most 00+ cars I've scanned and checked have a lean issue from the factory.

what exactly is "lean"? Also whats the difference between a powerlog and ported manifold?

whats better?

Lean is when your fuel trims are over +8, really lean is when you get a code. The problem comes in when your trims lock at WOT and you are doing 5K+ rpms w/o enough fuel. Pop goes the motor.

Powerlog is better. Ported exhaust manifold is not typically ported in the gooseneck where it matters.

So next time i go into ZZP i am going to get a FRONT POWER LOG.

Are these easy to install, the guy said that it was a 5 minute job??

5 mins if you know what your doing and the front manifold has been off recently. However, that's rarely the case. Studs rust, things are in the way, etc. Figure 30 to 60 mins. It's a bolt on mod so you wont need to modify anything.

All i do is take off the bolts, take off the OEM manifold and just bolt in the new manifold right?

sounds real easy, however my manifold does has rusty bolts, will this be an issue?

Get some good penetrating oil and start spraying them now. There are 6 bolts, the 2 outside studs will stay in the head, one bolt holds the dip stick on, you need to remove the nut, then the stud. The dip stick will be a pain but can be worked around. The 2 studs at the cross over pipe might brake, so pick up 2 new studs before hand just in case.

This is for headers, but should have all the info you will need.
https://www.gmforum.com/t278804/

All I can say is Liquid Wrench..lot's and lot's of Liquid Wrench!