I took a whole day to pipe test on my FMS. In my opinion the 41020 will be too long. I ran the 9853SS/41021 with sucess, also the 9853SS/41005 was better in my opin. I liked the 9886/41021 also and my favorite was(don't look Monty)the RE10 Losi pipe. BUT, my engine had all the sleeve timing bumped down some to achieve better bottom end by a modder. So my results may be unique. Testing was done in truggy. My friend did run a stock FMS with the 9853/41020 and it was ok.