[Hammer]

Headers are a PITA to work with on the modular stangs, plus unless you're heavily modded, HP per buck is pretty low.

Since you're in a emissions free area, I'd go with an off-road X-Pipe with a set of Dallas Mustang MIL Eliminators.

Finish it off with a Dynomax or MAC cat-back system.

A lowered car shouldn't be a problem unless you go with long-tube headers at a later date....