Hi Rc nightmare fans...

I just recently recieved a nitro rustler. It was running great through break in and now ive started tuning. everything was running fine until today. When i was accelerating it would get up to speed and then cut out. Im pretty sure it would be my low speed needle because i see alot of smoke coming from the exaust and it runs fine. It also has a trx 2.5 engine in it. I lost the black piece on the very top of the engine, would that be an issue? I am very scared right now and do not want to wreck it already!! please help!!!