SR won't idle

[NoStickers]

When I try to start my engine, it revs to 1500rpm for 5-8sec then drops to 500rpm and bounces there for a few seconds then stalls out. I can't keep the engine running by opening the throttle when the rpm falls to try and idle. The throttle does work when it shoots to 1500rpm on start up but regardless of the rpm it still falls to 500 after 5-8 sec and stalls out.

The engine did run in its stock form perfectly for about a year and a half. I upgraded the turbo/exhaust, new valve springs, valve guides, valve job, 264 w/ 11.5mm lift hks cams, new mafs, enthalpy ecu tune and 850cc injectors.

Please help me I'm stumped.

[NoStickers]

Anyone?

[180fan]

vac check first. if that don't do the trick, might be your iacv. if that don't do it, check over the mafs wiring.