hey guys im just wondering for in the future when my trx 2.5 engine craps out, that engine should i get? i think something with a little more power will be needed but not ne thing big of a change. i think the OS engines are a good brand but if you guys think the os brand is good then what engine is good for a nitro rustler? the .18 size? and btw what size is the 2.5 trx? .15? they just use a diff unit for that ?