OK if you don't know i haven't used the nos kit so don't jump to anything just yet! lol i have had this problem since i bought the car i just was to lazy to work on it anyways, if your driving down the road in my car and you ease the gas slowly it will reach to 7rpm but if you step on it it will fall on its face around 3 or 4rpm the car did have a gas leak when i bought it and the cel was on cause of that but i fixed the leak and reset the ecu i drove it for like 2oo miles no lights or anything,i noticed the sputter gets worse the lower the fuel is.if i put almost a full tank of gas in it it seems to run and pull good but once it gets a little low it starts the problem agian.maybe a fuel pump? idk

 

sounds like the pump is going bad. it will also do it the hotter it gets (longer the pump/car runs) easy enough to test the fp.

 

yeah i have to agree with shawn 100% ...also if you have an aftermarket fuel pump(high volume) and when you have it on the street do you ride around on a 1/4 tank or lower often....that will burn up the pump pretty quickly!