dies, hard starting

My 1992 PA has an odd problem. If I don't let it warm up to normal operating temperature before I drive it, it will die on me while driving. It dies within 5 minutes and is quite hard to get started again. And, if I drive a short distance without warming the car up it's very hard to start again. It starts fine when cold. It runs fine with plenty of power and will start normally if i do the warmup chore. The only thing i've noticed is that there's a vacuum leak that i can't find. the sound comes from on top of the engine and all the hoses are connected and i can't find any cracks in them, and can't pinpoint where the sound is coming from.
It has the standard PA v6 engine. the air flow coming from the interior air vents is very poor also. The only thing I've done to the car is put in a new air filter.

The best way to find a vaccum leak is to use a propane torch, (do not light) and with the engine idling move the torch end (with valve open) around all your vacuum hoses and throttle body. If you have a leak, the engine will increase RPM when it gets a whif of propane.

The best way to find a vaccum leak is to use a propane torch, (do not light)

Whoa, carb cleaner is a lttle more user frindly. Never heard of that one before, makes sense, but in the wrong hands.............

I have been using the propane method since 1964 with no adverse effect. Carb cleaner is a liquid and dissapates slower. You also risk the chance of it dripping on the exhaust manifold or around a plug wire that is missfiring.
Brake cleaner also works, however both are highly flammable when they vaporize.

Agreed on all accoutns.

However, propane is also HIGHLY flamable in vapor form in a confined area.