OK guys, all this talk on here made me go ahead and order a 21-5K with the HES mods and R2R break-in, now just to wait on it to get here

The website suggest a 063 pipe, It looks like on here a 053 pipe is best, which one? And I have a almost new RB2045 pipe, wouldn't that work as good or better than a 053? it is the pipe of choice for 5-7 port RB's and they are Nova based engines.