Where would I check for airfow and vacuum problems in a 1994 chevy Astor van.

SOURCE: 1994 gmc safari

Sounds like your Passlock security system went into the tamper mode. If your dashboard security light blinks when the ignition is turned on, your Passlock security system is disabling the injector module, preventing the car from start. Try this:
1- turn the ignition on and just touch the starter, without getting the motor to fire, then leave the ignition in the "on" position. The security light will blink for about 10 minutes. When the light stops blinking, turn the ignition off and leave off for 3 minutes.
2-repeat the step #1, 3 or 4 times. You will know that is fixed when you turn the ignition on and the security light does not blink, then the car will start. Make sure to stay inside the car when you're doing this, as opening the doors will trip the security tamper mode on again. Once the tamper mode is off, the car starts and opening the doors will not trip the Passlock tamper mode.

SOURCE: Electronic Control Module Installation 1994 G20 Chevy Van

I just had the same problem. If it is a regular van try under the driver seat in a plastic box. If it is a conversion van try in a pannel just behind driver seat on side of van wall behind a pannel that looks like a vent.

SOURCE: 1994 Chevy van brakes grabbing

try replacing the brake hoses they may have a restriction causing

SOURCE: 1994 Chevy G20 Van - Van (auto trans) only has high (D) gear

Sound like you're going to need to drop the transmission pan so you can replace the filter along with fresh transmission fluid. I had a problem like that many years ago, this correct the problem... I also know that the throttle positioning sensor will also cause transmission shifting problems. I would start with the filter change then go from there... Good luck.

SOURCE: what is the spark plug

Depending on what motor you have.The 2.5 is 60 thousands and the 4.3 is 35 thousands.Hope this helps.Good luck.