Ok so I had a problem a few weeks back with my cat coming apart and causing my engine to run very poorly. I get home after 2 weeks on the road and have my new high flow cat and new muffler installed. It acts fine for a few days,now its having this damn problem I cant seem to track down. It will idle fine for a bit till it warms up a little. Then it starts missing and sputtering almost to the point it wants to die, then something happens and it revs up a little on its own and clears up and idles back down to normal. Then proceeds to idle fine for a short time.

Also sometimes on decel I can feel the engine miss when I go to accel again its very prominent. Ive checked all the vac hoses. I have the neon coil swap(good fire at all plug wires). Just got new plugs today(NGK Platinums, had Delco Platinums in it before, 3000 miles old). Old plugs didnt look terrible but replaced anyway. I swapped ICM's and relocated away from the heat of the head.

I couldnt seem to find many answers to a problem quite like mine using the search tool.

If someone can chime in with similar issues or knows whats going on.

Engine throws a multiple cylinder misfire code after missing for quite a while.

Car: 98 z24 113k miles,manual trans.

Thanks in advance