Recently when driving ive been noticing on moderate acceleration and cruising speed with turbo spooled a surging from turbo/exhaust. Sounds as if variable veins in turbo are opening/closing slightly. Some noticable surging can be felt. However no noticable variation in engine RPM on the tach. Im about to take it to the dealer just want to know what to expect/try to scam out of my ext warranty....any advice would be great.