idle problems

it just started earlier today. it doesnt want to idle for shit it lops down to just about to shut off then goes back up. i tried vacuum lines but no progress. i have the weber 38 on a 1990 pup 2.3. im thinking it is the intake gasket but i am new to isuzus so if anyone can help it will be appreciated

the intake gasket is a very common problem on these trucks

will a collapsed vacume line have the same result

i sprayed around the intake and it didnt do anything though. i have spent days on it and got nowhere. but i am going to changed the gasket and the fuel pump this weekend.