very new to this so here goes

first off ill start with its a 2000 audi a6 2.7t 6spd Quattro the problem is interesting
driving around town or even on the freeway at normal speeds or under normal throttle it runs great even when I give it alittle more gas its very responsive however when I try to accelerate heavy it will sputter and lose all boost then I let off the gas and accelerate alittle slower and it will regain boost hold and be fine it only happens when I try to get some power out of it or when it is under heavy boost I have replaced both dv valves I had a check engine light when I bought the car for bank 2 sensor 2 o2 sensor I replaced that one and the bank 1 sensor 2 (so both downstream 02 sensors have been replaced ) check engine light whent away and I have not had it come back so I'm alittle stuck

other odd problem that recently started and I don't no if it cause the oil is just about due for a change or worse but when I'm cruising at night and its quite outside and I pull in 2nd gear I can hear what sounds like the turbo almost rattling ? it spools but for like the first 500 rpms it will kind of rattle so I'm stuck and would love some Imput !!