When I bought my car it boosted fine. I bought a auto meter pro-comp and it read a steady 10psi. Now I have chipped the car (apr) and when running from a stop light it will boost all day to 15 psi through all gears no problem but sometimes when I punch it in midrange or if I do it but not all the way without pushing that button in like downshifting one gear but not two it will sometimes only boost to 10 psi or it may boost to 15 for a second and then kind of jerk back down to 10 like when your under high boost and you let off all of the sudden. I just don't understand why i can punch it from 0 to whatever and it makes a steady boost but when I get on it another way it goes into the stock boost setting. Could this be a wastegate problem, diverter valve, mass airflow, computer? Any advise would be appreciated.