
Maximum PSI has various turbo kits for the S54 that work on the factory DME. From stock internal setups to built motor turbo applications they have you covered from top to bottom. Just earlier this year they hit 900+ whp on a stock internal S54.
The example in the video below belongs to BimmerBoost member @DocCarbon and it is not making 900 whp. It is a stout example though:
Max Psi Turbo kit - Precision 6266 @ 19-20 psi
ID1000 injectors
Radium engineering surge tank
2 walbro 485 fuel pumps
Exhaust cutout
Apex 17x10 with 275/40/17 M/T et street R on the rear.
RTD V2 mini shifter
Suspension and subframe reinforcement
As for the power output you have to ask him but it's definitely strong and definitely at 700+.
No fancy DCT here or even SMG but just rolling your own gears. He goes up against some strong cars and wins some and loses some.
For context he blows away a stock Hellcat but loses to a 900+ whp Hellcat. Some great runs below.