Should I have replaced the exhaust seal(donut)?

[apexjeepinjoe]

I just got done with the ax-15 swap and my truck started right up and ran good. As it warmed up it seems at the idle keeps going up and down and I seem to have the tractor sound before I shift when going down the road. I am guessing when I re installed my exhaust I did not get the pipe lined back up with the seal. Should I replace the seal or should I try to line up the exhaust pipe again?

[MJRemi]

If the seal isn't misshapened, re-use it. If you think it's too old to keep the seal, replace it. They don't cost that much.

[cruiser54]

They take a "set" so replace it since you're gonna pull it down.