what could cause backfiring when you rev the engine on a 1989 740 GL?
if i rev it up the engine will backfire several times....rich running?
what could the problem be and whats the most likely cause?

any help/suggestions are greatly appreciated!

thanks,
-sal

Small hole in the exhaust is a very common backfire. maniford, downpipe check first

Also if the car is out of time, how is it running?

crossfire throught the distributer cap is also common, look for carbon tracking inside the cap.

A bad ignition wire can cause backfire, again you should notice a miss on acceleration

another thought was the timing? can i use a timing light to check it? what should it be? or maybe could it be not enough back pressure? (i dont have a cat, muffler, or resignator.

thanks again!
-sal

could it be the radio relay? (whats it called)

If it's running way too rich, I would suspect the fuel pressure regulator. Pull the vacuum hose off, if it's got gas in it, there's your problem.