S4 stuttering problem
 

So just today my rx7 has started to do stutter under acceleration. Theirs a big decel in the middle acceleration. Happens anywhere from 2500 to 6k but is pretty predictable in the way that itll happen about every time you smash on it. Its dangerous and annoying and just started after i put a brand new non leaking water neck and bolted on a catback exhaust and gutted the cats.

S4 stuttering problem
 

The first thing to do is check and replace BOTH the fuel filter (low on the drivers side firewall) and fuel pump sock (located physically on the pickup of the pump). At this age the pump sock is usually filthy and there may be a bunch of crap floating around in the bottom of the gas tank. Especially if this car has ever sat for a prolonged amount of time in its 25+ year life.

Also, check pin 2I of the ECU, Green/White wire, w/key to on. Should read 2 to 3 volts on the cold engine and close to .5 volts fully warmed. You might has loosened or damaged the connection to the water thermosensor when working on the car.

The maf sensor plug was loose-_- lol its missing the metal clip so can wiggle free when it wants. And yes cleaning/ the tank pump and filter would be wise since im switching over to running premix soon