Need Help Wiht My Gtr!

[gajadojaja]

Hello everybody i own a R32 GTR 90 model and it is a Japanese circuit car which is heavily modified that i registered here in Brisbane. last night i was driving for about 5 min from my gf house adn i stoped at the lights and it turned off it did that about 3 or 4 times and when it finally stayed on when i was driving up until like 4500rpm or 5000rpm it runns very very shaky and it feels like its backfiring non stop and when i came home i noticed that it was smoking (black i think) on idle . Does anyone know what my GTR's problem could be? If it helps iv got like so many mods but ill give u some like the GReddy GT intercooler 700/400/103, Stage 3 CAMS, NISMO N1 Turbos, 3.5inch from turbo and 4 inch cat back exhaust, HKS F-con V pro gold engine managment comp, and so on. if somebody could please HELP ME it would be really appreciated.

Thank You!