20v blacktop extractors. Get a second flange made up to space them away from the starter and run a gasket between each. Then pull the studs and replace with either TVIS intake manifold studs (they're longer) or just long bolts.
2-1/4" from the collector back.
The best muffler I ever had was from my HKS AW11 exhaust. It would be similar to most baffled straight through mufflers.
This style is good:
Or the same style with the inlet and outlet offset from eachother with a small chamber in the middle.
Couple that with a Fluted coby before the muffler and you should have a good sounding, free flowing exhaust that you can live with.