Hello, please let me know how much RPM are the allowable for the stock k20z3 oil pump? is neccesary change it for the k20a2 oil pump? mods: header, cat back, intake.

Thank you very much

 

Balance shafts are what's the limiting factor. The pump will cavitate and/or risk explosion around 8500RPM.

This would probably be worth a read (I've only skimmed it): K-Series Oil System Upgrades - Under Pressure - Honda Tuning Magazine

I wouldn't go above 8300, maybe 8400 on the stock Z3 pump. If you want peace of mind, yes, I'd highly recommend swapping it out for a new a2 pump. Those can handle upwards of 9K all day long. Keep in mind of course revving the **** out of your engine is pointless though unless you're still making power up there, but that's all in the tune and what your engine puts out.