Definatly sounds like boost creep and fuel cut which is common when re-locating the the air filter to the front, 1) I would definatly get the wastegate ported on the turbo to eliminate boost creep, 2) get a FCD and FPR or an aftermarket self learn ecu which will remove fuel cut, speed cut and raise rev limit etc 3) change your manifold to an aftermarket one if you are still using the stock one as 1bar on a stock manifold will kill your engine eventually i.e melted 3rd piston. Hope this helps!