I bought my HMF slip-on for my Raptor 350 from motosport.com. I did a lot of research before I bought it, and the HMF suited my needs better and was the best bang for the buck. The White Brothers E-series makes the most peak horsepower but in my opinion they are ugly and sound like doo-doo. I opted for the HMF because they look good, sound awesome, make good power and back then were only $200 for the slip-on. To me, the Yoshi's are overpriced, and around here everybody and their mama has a FMF, I wanted something different. I had a DMC on a Warrior that I had one time and I think it made it lose power and it sounded worse than a White Bros.

You can get a Dynojet kit from anywhere, I use ronniesmailorder.com for alot of parts, they are slow to ship but their prices have been hard to beat so far.

If you measure the inner diameter of the stock head pipe and the inner diameter of an aftermarket pipe, they will be about the same. A larger diameter is where you would gain power, so if they are equal in size, and everything else being equal, then you will gain no power. The stock header is not more powerful, just equal in power. This only applies to Warriors and Raptor 350's. On most other machines an aftermarket headpipe would give it more power because the diameter would be larger.

 

The 25 pilot and the 150 and 152.5 are main jets you only need to change the main and pilot
Also keep an eye on ebay for an exhaust ive bought a few for deals first was a fmf megamax then a pro circuit then i got a curtis sparks and now i just switched to yoshimura

 

id put a hmf exhaust, and a big gun rev limiter, if i was you and your so worried about stability and shocks get the yfz450r, just becasuse the raptor is a 700cc doesnt mean its faster, its only faster at the top end of the motor and raptors are extremely tippy because of their height. o and a good place to buy parts is ebay, and rocky mountain atv.com.