Hey guys, I'm building a Worksman Adaptable tricycle into a motorized trike using a 212cc Predator 6.5hp engine I have a very thorough knowledge of bicycles, but pretty much haven't got a clue about engines apart from the basic mechanics of how they function. I'm getting a Predator from Harbor Freight and purchasing all the other gasbike.net trike kit parts from ebay/amazon. I aim to use this trike to commute to/from work, I'm aware it's not street legal. That's why I'm trying to be as discrete as possible about it. Planning to cruise at ~15-20mph in the bike lane with lights/reflectors and follow traffic laws to appease cops. I'm posting here because I need some advice. I want the engine to run as quietly as possible since I'll be in traffic. I was wondering if it's safe, in terms of backpressure and stuff, for me to only install an aftermarket exhaust pipe and muffler. Down the line, I do plan to also get an air filter and re-jet kit to improve performance, but I was wondering if it's safe to wait on those and for now just run the engine as is, but with an aftermarket exhaust & muffler to quiet things down. Thanks so much! Plamen PS: I don't know how to pick between the hemi and non-hemi, they are the same price and I've heard hemi is slightly better stock, but non-hemi is easier to upgrade aftermarket?