Like the title says..Only once you get in 3rd gear it hits 5800-6000 rpms and stumbles like it hit the rev-limiter then drives through it..It make salmost like a poping sound and it defintily is missing or extigushing the spark for some reason...
No black or blue smoke,no pinging (audible)...

Here is what led up to it.
1) installed J&S safeguard incorrectly and thought I blew my ECU
2) removed J&S and purhcased and installed new ECU
3)ECU wasnt bad turns out it was the ECU RELAY,not fuse (which I checked)
4)got it from dealer and didnt run it past 5000 rpms due to 9lb pulley
5)reinstalled J&S correctly this time
6)raced an SVT Cobra and car stumbled at 5800-6000 (beat him anyway)
7)bypassed J&S..installed 7 lb pulley..Still stumbled
8)removed J&S and soldered the coil wires together..still stumbled...
9)replace plugs..Still stumbled...
10) re gapped plugs from .035-.030- still stumbled...
11) swapped out MAF sensors..Still stumbled...
12) tried to put original ECU back in car but it wouldnt turn over.I guess it needs to be re-programmed to the key?


Tommorow Im going to try to swat out coil packs form a donor car..The car runs good all the way through thr RPM band until 3rd gear @5800 then it burps and keeps on going....Any I deas whats going on??

On a side note I checke my oil today and was down to 1QT!!!! Im not smoking at all and I kind of suspect that POS Stillen oil coole may have a leak..I last changed my oil in July about 2800-3000 miles ago..Any Idea WTF is going on???

 

dont know about the stumble, but I've used 3 qts in the last 2000 miles. excessive consumption is proving to be common, even more so in FI

 

I can say its definitely NOT the plugs,gap,J&S or the MAF...The only thing left different in the chain is the newer ECU which what could be the problem with that? Other than that I think the J&S may have damaged my coils...But I thought coils either work or dont..

Its very weird..

 

I cant remember, is your car an auto? I have seen this in another s/c auto (not that it really matters). It was a combo of the plugs and fuel.

 

Motor slowing taking a dump? I heard you get about 6000 miles outta a "boosted" 350z motor. Something about blowers? Thats what I have heard no telling if its the truth or not?

 

Well Good news!!I figured out the problem..One of the coils were bad...We swapped them out with oru wrecked Z and everyhting runs fine..I know Im going to get flamed for this but I 100% believe the J&S unit caused my problems, they all started the day the unit arrived..I know someone is coing to say "well what about the botched install" well #1 the instructions were wrong on one of the coil wire colors and #2 the connection method is sub standars as the coil wires somehow loosened and crossed causing the ECU relay to fry..I read things about the J&S unit causing coil problems in some cars but didnt believe it till now..I hope John from J&S reads this thread caus he needs to re-work the unit to work properly with the VQ motor.