A few upgrade questions

**dirtmaster88** · 11-24-2009

First off I want to say that yes, I've read the "Safely Modding Your 3800 Powered Car!!" sticky.

I have a 2004 GTP CompG (daily driver) that my goal is to drop the pulley size and then stop modding. So far I've done the following: K&N Cold air intake, 180 tstat, ssac headers, zzp flex pipe, high-flow cat, autolite 104s, autolite wires.

After recently putting in the 104s, my gas milage dropped significantly. I'm averaging about 16-17 mpg right now. I was 20+ before. The exhaust smells very rich. I am planning a 2000+ mile trip in December and would like to get this taken care of. With the mods that I've done, what pulley size would be recommended? Also, would getting a mail order PCM that's been tuned for a smaller pulley hurt anything if I kept the pulley stock for now? I'm thinking that the PCM will help out with my gas mileage issue.

Also does anybody know any solution for the P0420 catalyst converter code? I'm assuming it's from the high-flow cat. We do have emissions here, I was hoping this code wouldn't pop up

Thanks Guys

**ZR1Vette09** · 11-24-2009

hmm i've heard the 104's shouldn't be used unless you go with a smaller pulley anyway or else they will hurt gas mileage

**blueguy** · 11-24-2009

Tune + Pulley = WIN
Tune + Stock Pulley = Alright
Pulley with no tune = FAIL

Reason you are getting craptastic gas mileage is because 104's are for a smaller pulley setup. I mentioned that in there too.

**ZR1Vette09** · 11-24-2009

cool so my thoughts were right. BTW, dirt, how'd those SSAC's fit once you got them in place?

**dirtmaster88** · 11-25-2009

They fit pretty nicely especially since they were used. Had a leak in the crossover but was able to take care of that with a higher quality band clamp and some elbow grease

Any suggestions for pulley sizes with my mods and also thoughts on the code the cat is causing?