my tbi firebird just developed a problem...yesterday while driving down the road it all the sudden was down on power and idling slightly rough. i pulled over but decided to drive it home.....so far ive found the following things....extremly rich exhaust smell...rough idle like it has a huge cam....i have a small exhaust leak at the manifold-to-cylinder head on the passenger side that i havent yet got to replacing, ive only done the drivers side...i may try spark plugs but this was really weird and sudden. i hadnt started it for 6 days before but it was alright for about 20 minutes. lacking power because of it all...is there any sensors that you guys may suspect...also coolant is leaking outta the little round thing that the heater core lines go into in the engine bay...while i was in there today i noticed the vacume line to it was broken.

 

Sounds like a fouled plug to me.

I wouldn't fool around with anything else like sensors or codes or timing until the plugs have been changed.