1 7/8 is overkill but its usually recommened in case you want to go FI later down the road. Doubt you feel a diff with NA setup. Prob talking a couple hp.
This wait is a killer. It doesnt help that my Honda just died and I now have to drive my wifes Jaguar for the next few months with the license plate QT JAG.
I was told that the larger primary tubes can make a typical bolt on NA car lazy. Any truth to this? I have also read on other forums the concensus seems to be if you are under 600hp 1 7/8 is overkill. I am still trying to decide what I want myself.