one of the nuts that connects the manifold to the tail pipe has come loose and is making funny noises with my exhuast every time i hit a bump. what size nut fits on those studs?

 

Your 1991 will probably be 3/8"-16. I know RENIX is, and I don't think that stud size changed (although I'm not quite certain.)

If you can, get brass nuts. Before you put them on, round off a cold chisel on your grinder and give each nut a firm whack with the thing - enough to deform a thread or two and the end. Then, install the nuts with the deformed threads going on last. This is probably the single best way there is to make sure those nuts stay put...

Don't bother with split lockwashers - they don't work worth a damn. Star washers are only marginally better in this application. A deformed thread locknut is best - and you can make that yourself.

 

thanks alot for the info i look forward to hearing the sound of my flowmaster 40 sounding like it should once again.