Hey Muddy, I've got the O.S. T-2030 blue pipe. It is pretty much the only one that you can get right now that will work great with that engine. I called all around looking for the popular pipes such as the 2040 and 2050 but no one has them right now. There impossible to find right now. So I'd think of going with that one. You will have to buy a nipple for it as it does not come with one. As for what % nitro I will be running, I think I am going with 30%. I go to a track where there are some pretty serious racers and they also insist on me using this also. If I'm not mistaken, which ever % nitro you start out with that is what you want to stick with, don't change it up. I'm pretty positive that this engine is well capable of handling 30% nitro. And yes, I did notice that my engine came with an extra shim but I am just going to leave it off and see how it does without it. I may try putting it in there later on to see if I notice a difference. Hope this helps.