Ok if it's not the fuel pump, it might be injectors? What kind of condition are they in? How about the fuel delivery itself, could there be a restriction that allows low flow, but hampers high flow - like a second fuel filter without a lift pump?
My own car (D40, different to yours, but similar principle) has a silent turbocharger. I took the baffles out of my air intake and suddenly you could hear the sound of the turbo ... have you ever stood (this is dangerous) near the intake of a military jet that was running? That same sucking sound is what I hear when I remove the baffle along with a greatly increased ticking (induction) noise. Sounds like the timing chain is banging away, but it's just the airbox. I put the baffles back in - blissful quiet compared to what it was.
A larger exhaust (which often "loses" parts like the muffler
) will allow you to hear the whistle of the turbo. Having a larger exhaust (or removing the muffler) doesn't really give you a huge boost of power, but it makes the thing sound fantastic. A bit like the BMW K1600GTL (1600cc in-line 6cyl engine) - take one out for a ride, it's amazing. Below 3,000rpm and it's quiet as a mouse - not a lot different to my 1500cc 6-cyl (boxer) Goldwing. Take the beemer over 3,000rpm and it sounds like something just off a racetrack - you really do want to keep it in first all the time, and believe me when you're in first gear on a motorcycle weighing under 300Kg with 160 horsepower ... you know, without a shadow of a doubt, that there's a lot of power at your fingertips. I wonder if it's similar for other modified-exhaust vehicles - do people leave them in lower gear to get that great sound, and discover that performance is improved?