my y pipe conundrum
 

here it go recent purchase a motordyne xyz pipe straight pipe replaced it my oem y pipe (2003 350z) so yesterday went raceway here my best time for day was:
xyz pipe:

60' 2.068
330' 5.750
1/8 8.755
mph 83.195
1000' 11.314
1/4 13.494
mph 104.567

best time with oem y pipe

60' 2.138
330' (it was left blank on the slip)
1/8 8.848
mph 82.378
1000' 11.404
1/4 13.581
mph 106.142

now question is even though got fastest E.T. with xyz pipe trap speed constantly lower then oem pipe do guy think that i should put back oem y pipe or leave the xyz pipe on? (planing get car tune with Osiris in couple week from now do think benfit more with xyz pipe over the oem?)

Have you dynoed with both set ups or at all? Some torque may have been lost removing the oem y-pipe

nope havent dyno both set up

well ur trapping slightly higher with the xyz pipe in the first half than with the oem y pipe, unless u messed up or something in the second half idunno . also the reason ur E.T is faster with the xyz pipe is because u launched better .
best way to compare would be to dyno with it on and off back to back.
could also be that since the xyz pipe exit is 3" and the rest of the exhaust is smaller diameter, i just recently completed my exhaust all the way back since i too had just the xyz pipe with stock mid pipe and muffler, when i installed the rest of the exhaust it felt a lot better especially top end