I went ahead and ordered the Pypes system with the Race Pro muffs. In doing some research, it seems like an excellent system for the money although there is one possible draw-back...the Y-pipe inlet on the Pypes system is much smaller than that of some other vendors systems. the inlet in the GN1 system is HUGE!!! but probably overkill for a mildly modified car like mine. I installed an ATR dual 2 1/2" system on my previoius GN and the Y-pipe inlet on the ATR system was also *very* large. Someone posted the inlet dimensions on the Pypes system and the height of the oval is less than 3" which means you're going to have an abrupt transistion in pipe size if you're running a 3" test pipe or cat. Such an abrupt decrease in size *IS* a restriction although I don't have the means to test how much of a restriction so I don't know if it's significant at lower power levels. This can actually be calculated but I'm too lazy!

I'm running an old ATR 3" downpipe and testpipe so I'll measure the difference in opening sizes between the outlet on the ATR testpipe and the inlet on the Pypes system - I'll post results in this thread.