I'm kinda' with Cab on this one.

If you already own the Perf RPM AND it fits under the hood with no major gymnastics, I don't see any downside to using it.

But, if you sold it for anything close to what you paid for it that money could be used for something special, like diamond earrings for the wife. Or a new driver. Or a very nice dinner.

It's your choice!

R.