Rouge, I put an OS carb and header on my stock .15 FE engine, as did Divine are we both "stupid" for not just buying a brand new engine because of a lacking carb and header. Did you jump right in, pull out a perfectly good engine and buy an OS just so you can say I have an OS in my RS4. ( my guess is you got it used with an OS already in it) Alot of people have trouble tuning a nitro engine. I never implied the guy was stupid, only that he should learn the basics of nitro engines and tuning before buying an expensive engine. What happens if you lean it too much? BOOM. I'm sorry you feel the need to be confrontational when we were just telling him a good starting point. And if you think HPI solved anything with a one needle simple carb, well then more power to you, I'll sell you the one I took off since you think they are so great. So why does HPI show a two needle carb upgrade right in the maual that comes with it? That carb is junk, how can you possibly tune the car to idle well, take off good, and have good top end with one needle, there has to be a compromise, maybe you can explain this to me? Is it simple to contantly have to mess with the throttle trim just to keep it running, is it simple when it sits at idle, loads up a chokes on excelleration, hmmmmm I think not. So exactly how is this one needle simple carb better? BTW you are not the only person here with "experience" and from your post and your tone I seriously doubt how much experience you actually have. And you DID take my first response to you wrong, I guess some people just can't handle constructive criticism