I say go with the heads and cams,because NX,NOS,or any other of those nitrous companys products will destroy your engine VERY fast if you use it often(like once a week).Thats because NOS hits your piston right as it hits TDC and instead of INITIALLY blowing it down with the rotation,it hits it when straight up and down(TDC) and puts a TON of load on the crank and rods for a split second until it passes TDC,then it blows it down.NOS has a bad habbit of blowing out rings,because of the pressure it puts on everything.I would NEVER put NOS on a car with more than 75K miles,most reccomend not to do it at 50K,and this is because your rings are old and can EASILY blow.Your car would last MUCH longer without it and just slapping on some heads and cams and mabe a few other things so you make sure you kill him,besides if I want to beat someone,I would rather do it by NOT cheating.Some may say SCs are cheating,but your moter still has to turn it,same for turbo,but NOS is just spraying a mixture into your cylinder,and the motor does not have to work for it.Also the power is always there,and you NEVER have to worry about filling a bottle(think about how much money you would spend filling the bottle over the years{if your car ,made it that long},ALOT),and what would really be annoing is if you forgot your bottle was almost empty and then raced a mach 1 or something,and just as you start to pull a car on him,your bottle runs out and he blows back by you.Anyways thats how I feel about it,so I hope you take my advise and sove yourself a ton of trouble.BTW that big shot who sells NX will just make up excuses so he can make you a sale,and try and convince you that every thing will be fine,as long as you use a 75 shot or less...well that is untill you bring him one of your pistons a few yoears later (might last that long if you go with a 50-75 shot and you hardly ever use it.Remember though,NOS can NOT hurt your car if you never use it,but it is worth $600-800+ for a one time/or seldom use against a few cars?).