I've had nothing but bad luck with mods on my '04 SS.

First the low resistance plug wires were a flop. They worked great on my old 5.3.

When I first put on the UPD, things were great. Two or so weeks later (this weekend here) I noticed that I didn't quite have the lowend power that I used to. The truck was starting to act all "hit or miss" as to how it ran for that particular day. A lot like the plug wires were.

I put on my factory intake, and the thing runs awesome. Pulls nice and smooth everywhere, with a nice powerfull hum. Things even went as far as getting better shift points and lockup kickdown points. It makes me look back at the UPD, and think that it wasn't carbureting correctly.

Just how good is the computer at tuning the A:F ratio after a mod? It seemed to only take 50 miles to get things back to normal with the stock intake, but seemed confused over time with the UPD.

I know the '04's are having some problems taking aftermarket programs due to OnStar and such. Think GM also put their hands in the programming, making the computer less able to adjust correctly?

Maybe the TM settings on the SS are RIGHT on the verge of stock power? Any additional power, and I'm hitting TM?

I'm starting to really feel as though I need to tune with a wideband and Edit to get the most out of a simple mod like an intake. That's pretty frustrating. Anyone else running into problems like this?

 

Interesting you say this. I have an '04 GMC, and although I do not have a UPD, I just installed an Airaid this weekend and I am putting the Magnaflow put on as we speak. With just the airaid I think there may be a slight loss of power on the bottom. I thought when I first got in the truck it might have been me, but after reading this is am starting to wonder. Maybe the pcm takes time to adapt??? I have seem my induction supposedly make 12 @ the wheels, but maybe I need to get the rpm's higher to feel it, and then again maybe I just lost some torque. I'm in the same boat...