Swank4

I've had a GIAC-X chip for a few months now. Recently, I noticed that my boost levels peak only to 16-17 psi (when floored at lower rpm) and then level off around 14-15psi (when floored during mid-hi rpm) and start falling to 10-12psi (at rpm above 5000). When I first got my chip the spikes were 18-19psi and leveled to about15-16psi and fell just below 15psi at high rpm. So, I'm obviously not getting the same boost now as I was before. I'm measuring boost by eye with my A-pillar Omori gauge. Also, I could swear that my turbos sound louder (more siren like noise) especially when cold...but that's more subjective. To top that, I raced another S4 on the street a few days ago. The situation didn't allow for a direct side-by-side comparison, but it was good enough. Basically, he pulled on me through 2nd and third gears fairly strongly. Everything on the outside of the car looked stock, so I'm assuming he just had a chip. I didn't get a chance to ask him. Seeing as I have the GIAC-X, I'd think that another chipped S4 shouldn't pull like that.

Well, what have I done? I decided to let the dealer take a look at the car since my 20k service interval was approaching. I swapped back the stock chip last night and drove the car around a bit. The boost seemed normal - spikes to 9psi and leveling off to 7psi. So, the boost hasn't changed over the months at least with the stock chip.

The dealer said they didn't find anything wrong with the turbo system. I specifically asked them to check for intake and boost leaks and they said nothing was found. They said they checked the TBB and nothing was wrong. No DTCs reported.

What could be causing my loss of boost with the GIAC chip? Is it the chip? Or, could there be a leak that is only noticeable with the aftermarket chip but not the stock? Or, are the turbos starting to fail but are able to appear fine under stock boost levels?

Any ideas would be helpful. I'm going to try and get it in for a dyno.

Thanks, Carter.
Reply: cfields72@hotmail.com

Audi2ptzero

Over time a turbo will get worn out and produce less boost and less air flow.

If you have logged maf readings before, you might want to log them again and compare the 2 readings.