Classic/Antique Car Repair: 1991 Pontiac Trans Am, Rough Running, vacuum line, system diagnosis

Question
After taking our Trans am out of its winter sleep and giving it a general once over it was time to enjoy the weather and go for a cruise. The first 10 kilometers were great, then for no apparent reason the car started to buck and stutter, we pulled over right away and the only thing that was out of place was a vacuum line, after hooking it back up we were able to limp back home. At no time did the Service Engine Light come on, and there were no other indicators that something really major was wrong. My first thoughts are that my wife filled the car with bad Gas before putting it to sleep, or that the Fuel Filter may be Clogged. Could you offer other possible causes and solutions for this problem ? Thanks
General information about the car
1991, V8, 42,000 ( Original Kilometers ), no tuning or modifications have been done to this car, everything is original.

Answer
The first thing that I do to any computer equipped car with a running problem is to hook up a scanner and get readings on the various sensors and controls regardless of the Check Engine light on or off. Sensors can be out of range a little bit and cause a running problem without turning on the engine light. Then check the obvious like the spark plugs, wiring and ignition system. Diagnosis is a bit complicated and there are dozens of things that can make and engine run rough.
Brad