I've been reading a bit on vortec 5.7 builds, but most i've seen have either carbs or tpi. Is there any hope for the tbi for a 400ish hp build? I kinda need to keep a stock appearance since i live in CA and they are **** here. This is for a 1990 chevy van currently with a built 700r4 and a stock tbi 350. I know it's not a 3rd gen, but i assume there isnt much difference in the drivetrain.
I'm curious if i can get away without a custom tune, and is only an injector swap and/or bigger fuel pump needed?

I'll venture to say a 400hp CA emission build is not that easy.

400 hp tbi is definitely possible. You will definitely need a custom tune, cam, 454 tbi, headers, exhaust, etc. Mine has past emission test however we do not have a strict visual inspection. I have not had mine dyno tested but Desktop Dyno say about 400hp.

the main problem you would run into is no egr, so you would have to run an external setup..there is only one intake that has external egr provisions the gmpp tbi. so as far is intakes you are limited in choice

i have a pretty full machine shop, so is there any chance in modifying a stock vortec intake to work? I can probably get some california legal headers, but i really do not want a loud exhaust. I'm ok with loosing 15hp if it means i can maintain the stock exhaust, but do you think it will really be choking?

That GMPP manifold is really the only choice to retain your EGR. EGR will have to be plumbed to one of your headers which will require some welding. The stock Vortec manifold only works with that type (MPFI or whatever) of injection and cannot work with TBI. All of the other Vortec intakes are carb intakes without EGR. You will need a better fuel pump and bump fuel pressure as well.
For the headers you will probably need Hooker 2055's or the Headman shorties with AIR tubes and a 3" CAT to stay emissions legal as well.

I am running GM Intake 12496820 with a 454 adapter and 454 tbi. Has egr (externally plumbed)

You really need a good 3" exhaust system. Try Magnaflow catback and a 3" cat converter. Loud when you need it but cruise is pretty mellow.

I would look at Doug Thorley Tri-Y headers, 3" highflow cat, and a 3" muffler of your choice. Make sure you run a heated 02 sensor.

I would run the EBL Flash.

I would run the GMPP Vortec Q-Jet manifold and an early 454-Q-Jet adapter and 454 TBI unit.