I need advice on which pipe to get here are my choices:

FMF Titanium-4 w/Stainless Mid-Section $260
White Bros. E-Series Pro Meg $280
HMF $185
Pro-Circuit $190

Which one gives the most gains in the Bottom & Mid-Range, Which is the easiest to install, & Which one is the quietest? Also what does a smaller Endcap do?

 

I have the pro circuit slip on and I am very happy with it. It gives a good boost on the bottom end and in the mid range, and maybe a little on the top. It sounds AWESOME, but is a little loud! I have heard excellent reviews on the HMF as well. To me, the others you listed are over priced for what they are, but that is just my opinion. Had I not found a great deal on my Pro Cicuit, I would have gone with the HMF, they seem to have great customer service.

 

If you got the spare money, there is plenty of gain in the head pipe too. Most aftermarket headpipes have a better curve from the front, and less bends getting back to the muffler. The RWR is almost straight - substantial air flow improvement over the stock headpipe, and allows mounting of stock heat shield.
If you can't get a full system right now, get a slip on from a place that can sell you the headpipe later to add.
From what I've read of pipe shootouts on the Raptor and 400EX - the pipes all are pretty close to each other in HP, with the biggest differences resulting from inconsistant air box mods from one pipe to the next.
Never seen the RWR tested though.

 

For the price I think the Pro Circuit is the best bang for the buck. It sound awesome but like Gottahavaraptor said its "a little loud". I bought the quiet core for it and it does work but you loose most of the power you gained with the pipe. The pipe didn't take more than 10min. to install, very easy.

 

Ok, thanx anybody else have an opinion?
By the looks of it I'm going with the Pro-Circuit Silencer