I have heard that when one chips its car it is a good idea to also get a new exhaust to increase/reduce back pressure (not sure which one). Does anyone know if this is imperative and if so why it's important?

Back pressure is the pressure from more exhaust gases trying to escape through the exhaust system than will fit. Generally, less is better as it allows the engine to run more efficiently (doesn't have to fight to get rid of the exhaust in the cylinders). This is why most of the power gains from exhaust systems come at high rpm, that's where things are really restricted. However, some backpressure is required for propper operation, the engine is tuned to expect and utilize some backpressure. This is why the top end gains often come at the expense of low end power. The best bet is to go with a tuner who retunes your chip when you do the exhaust to take advantage of its characteristics, or someone who can custom tune the chip to your specific car.

It is not imperative to get a new exhaust when chipping your car. Although turbo cars are usually impacted more than normally aspirated cars by changing the exhaust as discussed above, remember the chip maker programmed the chip for use in a stock car (unless otherwise specified like a stage 2 chip).

Regards,
Rodney

'99 A4 1.8tqms

As the exhaust gasses are pushing the piston down, the exhaust valve is opening. If those exhaust gasses are pulled out too quick you loose the low rpm "power" or torque as the gasses now are no longer there to keep pushing the piston down. At high rpms you want to pull those gasses out so that no exhaust gasses remain when the piston bottoms out and starts its journey up, because the amount of time the piston is spending on one cycle is not as much as the lower rpms. Thus if you replace the resonator on the 2.8l you could loose low end torque.

Reggie

98.5 30vQMS

With a 1.0 Bar chip the turbo gets extremely hot. Based on my experience, the heat will eventually soak through to the intake side, leading to at the least a very noticeable reduction in power output, and at the worst, pinging.

I noticed that since I had my cat-back exhaust system installed, underhood heat has been reduced significantly.

Paul
'98.5 A4 1.8TQTS