do i really need a muffler??

Slant 6 sounds annoying without muffler.
I would go with any straight flow muffler.
Is Simons mufflers available in states?
I've had some good results with simons. Nice and low tone, but loud enough to wake up neighbors when flooring pedal.
Made even my first car, 1,3 litre Corolla ke30 sound like a 2,0. :-D