I've read a lot of the posts in this part of the forum, and in light of my recent topic lock for posting in a thread one month old, I figured I'd ask this question all over again.

First off, does a K&N Drop-in filter do much for performance on this engine? Is it worth it? Will it even marginally improve my gas mileage?

Second, I know the factory exhaust is "sport tuned" but would there be any gain to getting some better mufflers, say...flowmasters? I have a magnaflow on my regal and I noticed a bit of an increase in throttle response, but I figured I'd ask you guys what your experiences have been.

you might notice a small change with the K&N, but it will probably be noticed because you want to notice it, if you get my drift.

I only know of 1 person running aftermarket mufflers on their GXP

ReallyAGXP is running Solo Performance Mach 28'* stainless 3 inch in 3 inch out glass packed

Do you know if ReallyAGXP noticed any performance gains from going to an aftermarket exhaust? Its a really nice sounding exhaust, but I'm not sure if sound alone will be worth it enough for me.

Would anyone here recommend the removal of my resonator? Or would that cause the exhaust to sound too raspy?

So the consensus is that it wouldn't improve gas mileage or performance much at all to use a K&N filter?

I'm not new to cars, but I'm new to the GXP, so I apologize if these sound like elementary questions that I should already know the answers to. This is a bit more of a complex vehicle than I'm used to.

ReallyAGXP just vanished, so we can't really ask him.

your GXP doesn't have a resonator.

as far as a K&N drop in, you will have to wait for someone that actually did it in a GXP to tell you.


http://www.bonnevilleclub.com/forum/...light=mufflers

Don't feel like elementary school. At least not by yourself. Nobody has really done much with the GXP.

I would expect a good flowing filter to possibly give you around 5hp, but no more. I have no clue about the exhaust. I wouldn't expect it to change much other than the sound. I think a hi-flow catalytic converter would give you the most bang for your buck considering the exhaust flow at the higher rpm'* in the Northstar.

Would a high flow cat affect torque much? I've heard of reports of torque loss if there'* not enough backpressure.

5HP is enough of a gain for $40 or so. That would take me up to 280hp just for bragging rights.

When I get some more cash, I'll see if I can actually do anything with the GXP. I wonder if anyone will make an aftermarket for this thing in the next few years,

For now, my first mods will be HIDs on both fog lights and low beams, and a K&N drop in. We'll see what happens from there on.

Nobody will make an aftermarket for it until the PCM is cracked. If you have 5-10k laying around, someone might do that for you.

NO cat would lose low end torque, but the Northstar isn't a torquer, so you probably wouldn't notice.

A High-flow will suit you as well as it does us. You'll feel it at the mid-top end.

So could I just go for any high flow cat? A magnaflow high flow cat for example? How much would one cost me?

With a cat and a drop in K&N filter, what kind of gains would I be looking at?

I added a K&N drop-in the other day, didn't really notice anything. But then again you're not gonna notice 5 extra hp.

I'd go with a MagnaFlow 100%

a universal one should cost you around $60-$70 give-or-take.