fuel problem?
 

ok iam gonna write out a whole novel here so you guys can get somewhat a good understanding of whats happing...

i was driving home one day and i took a right turn and started to acclerate so i wouldnt get hit by the cars coming and than i got up to the speed limit and let off thah it felt like my engine had a misfire or something than the rpm guage was just going all over the place it would jump from 5k to 2500 rpm and just up and down than i pulled over and the car died and wouldnt turn over so i called my friend to tow me home and when he got here we tried to start it agian and it started with no problem. he suggested the fuel filter so i changed that out and yesterday it did it to me again! except i didnt pull over and i kept driving and than it the car was running perfectly again? is it my fuel pump? could it be the header i installed? (p.s. it has a brand new coil pack with plugs and wires)

It could be your fuel pump. When mine was failing the motor would stutter under acceleration.

Could also be the brand new coil pack - but the miata engine will generally idle on 2 cylinders, which makes the coil seem unlikely.