What's the loudest exhaust i could get for my Honda shadow 750ace?

What's the loudest exhaust i could get for my Honda shadow 750ace? - 1

Take off the exhaust pipes and run straight off the exhaust port.

Straight drag pipes would be the loudest. But in addition to sounding obnoxious, your performance will suffer. Motorcycle engines run much better with back pressure in the exhaust. Back pressure helps prevent cylinder scavenging which will cause backfiring and flat spots in the powerband. At the very least, run some baffles if not some good free flowing mufflers.

Hacksaw off everything but the last inch. Your neighbours will kill your bike before the valves melt.

Run about 2' of pipe straight from the exhaust ports toward your head, an inch and a half or so diameter to really get high sound pressure levels. It won't rumble, but will make you deaf in no time.