Scrantlanta

I recently purchased another B5 and have been doing some work to her. I've done full exhaust downpipe back APR intake APR stage one chip diverter valve and a bunch of maintenance work including full PCV valve and hoses and have the car gone through multiple times at a shop that specializes in Audi. Now I've spent thousands of dollars on this car and it has been in the shop four times and every time I get the car back it has a check engine light but that's besides the point. Has anyone had problems with the apr tune ? Since I've had it done when I accelerate not even at high-speed's but when the RPMs get high the boost drops and drops the RPMs back down about 2 to 3000. Doesn't seem to do it when accelerating at a take off and once I hit higher rpm's for some reason it just rolls high low high low. Now I don't think the shop has a clue what's going on and I would really appreciate some advice so I can actually enjoy my car instead of just driving like a granny. It's also a work vehicle so I would like to be able to have it be reliable. I can't even pass somebody on the highway without it dropping the RPMs out. Feels like it can't hold max boost. And just reverts back to running at lower boost and builds up again