<< i assume you then need a better grade of gas? >>
The stock engine is designed for 91 or better. Anything less and the engine retards the ignition timing, and you lose horsepower.
<< I've driven my friends A4 extensively, both before and after he chipped it with APR. Honestly, I may not be worth it. It does give more top end power, however it does nothing to the low end, and it still feels like pushing it would help get it off the line.
Simply put: no power until 4K RPMS. Before or after the chip. If your looking for bawls, you should not have bought the 4cyl engine. >>
Something must be wrong, because you are part of a very, VERY small minority. Actually, your experience is totally backwards from everything I've read. The chips increase low end torque which certainly makes the car feel head-snappingly fast. And they are also known for less-than-stellar performance above 5k RPM's, simply because the small turbo can't provide enough airflow at those speeds. Not saying you didn't experience what you said, just that it isn't the same thing thousands of other people have experienced with the chip.
<< but are there any other cars other than vws and audis that can get as significant increases by chipping? >>
Maybe some of the Saab and Volvo turbo engines would benefit as much, but I don't know anything about those cars. The key here is the turbo tho: increasing the boost pressure of the turbo is an incredibly easy and effective way of increasing horsepower by large amounts. Off the top of my head, I can't think of any other new turbocharged cars besides VW/Audi, Saab, and Volvo. Oh yeah, Mercedes Kompressor is a supercharger.