what is the consenus with going over 400whp without alky, n2o or race gas? all of the tuners I have spoken with say not to run any higher than 20psi on 91 octane. what is the silver bullet here?

Its doable with a big enough turbo and good tuning. dynojet power that is.

what type of turbo and how much boost?

30r or 35r will do 400 whp on 91

IMHO, A GT35R would get you there much easier then a GT30R.

35r wtih a stroker and 19psi will get you 400hp on the dot with 91 octane gas. that btw will be a slow arriving very boring 400hp.

i'd much prefer a 350-380hp from a 9 turbo with all rupporting mods.