2 seasons ago, I replaced the 454 in my Baja with a 383 mag stroker. Up until this point I had no trouble whatsoever, but coming in today, the engine stalled when trying to idle in. It ran perfect all day, got on it a little coming in but didn't open it up. Once I threw the throttle all the way down, it died. Now it won't start unless I give it gas, and it dies if I put the throttle all the way down. Its idling at about 600 rpms at the lowest before it dies, which is about normal. Now I'm hoping its something minor but it seems to never be. Any ideas? If its something I can do, I'd rather do it myself than have it in the shop for god knows how long.

Vacuum leak?

if its an MPI engine ,your having a bad idle engine module ( electric operated motor that holds idle at around 650 rpm)
mounted at the throttle body most of the time.

If its a carb ,it could not be difficult ,although itcould be a little time consuming to find ,see if you have fuel pressure at low rpm,s (5-7 psi at the carb )

I dropped it off today and the mechanic said he knew exactly what it was, and that was the idle motor is shot. He said he's going to run a test just to make sure but he'll have it done by Tuesday if it is the idle motor, which is great!

bad IAC