stock 2003 and MS-II
 

Will the MegaSquirt-II EMS System - SMD PCB3.57 help the performance on a 2003 LS miata?
It's all stock.

Just asking, I have one and was wanting to use it.
Once I save up enough mula I'll start adding fun mods to the car.2005

If you get it on the dyno, yeah probably, but I wouldn't bother spending coin on dyno time until you get some boost into the thing.

Definitely. I have an RB 4-1, header, 60mm exhaust, Monsterflow intake, fine-tuned MS-2, and saw 159hp at the crank at 7400rpm, and the car is blast to drive when you keep the revs up. Btw when it was measured when stock, it was 137hp at the crank.

Dimitris