I've owned my 2001.5 S4 since late 2005, over the course of these years the car has developed into a very well rounded car.

I built the car in my garage running a custom GT28 kit. Mod list is pretty small, All bone stock from the heads to oil pan besides the list below etc.

Rosten rods, new bearings with all the necessary replacement components when building any motor.
ARD Bi-Pipes
Vast stage 4 clutch
1 piece billet steel flywheel
Vast meth kit
Custom 3.5" exhaust fitted with 2 reflective resonator mufflers where the cats use to be and 2 regular mufflers towards the rear bumper.
Custom 750 Bosch single tip titanium injectors, AMAZING PIECE
4" Cold air intake with 95mm Maf
Vast custom pump file for now.

Car runs sub 3 second 3rd gear pulls, at or above full weight, no meth, on 93 octane, peak boost of 20lbs was reached around 3800rpm. More tuning with meth and upping the boost to 24-25lbs should be insane.

Surprisingly the car is very responsive and makes instant boost in all gears, almost hard to keep the car out of boost.

I've been in all size GT cars, RS6 cars etc and can't recall one being this well rounded, power band is 3400rpm to 76-7800rpms on 99% stock parts etc.

Will keep the progress updated, hoping for 525-540whp on the local Mustand dyno @ 25-27lbs.