I know the 2.5 is the most powerful in it's class and I was definitely not questioning your knowledge take my question as it is just a question. No insult intended I would be very happy if I don't have to spend more money on another motor. As I said I am very happy with the stock 2.5 I was worried that if I do the mods I am planning to do will I loose negligible performance. With the success you are having I might just save a lot of $$$$. The question with the .21s were that they were always too heavy to begin with. They might be perfect for 1/8 scale buggies and touring cars but they usually had a less than satisfying results on the monster trucks compared to the other 2 applications. I am sorry if you thought I was disrespecting you, I would never intentionally do so to anyone on this or any board. I have learned a lot from this board and would never intentionally berate or insult anyone, please accept my apologies if you felt dissed in anyways. Reviewing my previous post I now see why you would see it that way. I am very thankful for any input you may offer. I do have a question for you I B Racin. My carb settings seem pretty dialed in I would like to know what your carb settings are if you don't mind sharing that info. I need a baseline if I am even close to optimum settings. So far the 2.5 has been the most easiest and most consistent nitro motor I have tuned. I have 10 years of experience with nitro tuning but I would love to learn more from people with the experience such as yours. I had 3 choices for my first truck by the way. They were the Savage, T-Maxx and the upcoming AE Monster GT. The T-Maxx has the smallest engine of the three but still does not give up anything in performance, not to mention the better handling truck compared to the Savage. I based my decision on the test reviews. I did my homework before I bought the T-Maxx and all I can say was I could not be happier with my choice. The engine size did not discourage or even actually swayed me away from the T-Maxx at all. You are by the way absolutely correct about HP claims, they are there more for marketing purposes than anything. You have by the way pretty much got me thinking, I am now more confused than ever if I should spend the money on moding the 2.5 or getting a new motor, In your opinion or if you know anyone that has done the Sirio internal swap on the 2.5 is it really worth the $. One more thing do you know anyone that makes a bigger diameter exhaust header the stock one seems puny, even my .12 OS engine from 6 years ago had a bigger header pipe. what's up with that LOL. Thanks for the encouraging info on this mill, really makes me happy to know I made the correct choice, I was a little hesitant at first since I am a huge AE fan.