GDJT Allroad^2

How did you like the K03/K04 + GIAC + piggies?

I had K03/K04s in my '00 S4 w/ MTM and piggies... I felt limited by the ECU.

Nappy

I think I understand what everyone (s4 forum)was telling me to do. Stand alone MBC to bypass the N75/ecu and GIAC which is friendly to lemmi tweaks to fuel and timing. Should be good for up to 20psi. I never tried this route but I'm almost certain it would work. I opted to take the guess work out of the equation and went the K04 route.

GDJT Allroad^2

I was spooked by stories of how massive the K04 lag is over the K03, but the end result is that you should be able to create and sustain the same boost pressure with the K03/K04 hybrids that you would with the K04 setup.

The ECU just lets you get the air/fuel mixture right, but combine that with the bigger RS4 injectors and you're good to go with massive (20psi-range) boost and 400hp at the wheels.

I always thought the MBC just adds insurance (when put in parallel) that the the N75 won't demand more boost than it should, or if the N75 gets stuck the MBC is your failback.