changing fuel filter on 91 pickup

Tie a rag around your wrists so gas doesn't run down your arms? :-)

If you have a running problem, this probably isn't what's wrong.

what do you mean?

it does run rough at times and when i cram >

I say try it, it won't hurt. Here's a cool tip, Pull the EFI fuse while the car is running to use up most of the gasoline in the line. This will minimize spillage. You will be happy. Since Nissans are pains in the ass, if it runs bad, change plugs and wires if it hasn't been done. Change PCV valve (easy). And if it still runs like crap, it may be an emissions control item that's gotten messed up.

Just saying I bet it won't fix it. It's wishful thinking IMHO that this is the problem.

BTW you say "when i cram on the gas the RPM's just go high and i don't get much power" that's a bad clutch if it's a stick or a bad tranny if it's an auto car.