I've got an evo 9 mr that developed a very serious misfire. Doesn't matter what gear it's in, as soon as it builds any boost it cuts violently...

The car just had a full motor build. stock turbo, bc 272 cams, 1200cc fic injectors, walbro 255lhp, turbosmart bov, and is run on speed density at 20psi. Come tune day, we were making good progress. Doing pulls for quite a while. Then as we were finishing up, the car began to cut violently, not taking any load what so ever. The tuner added more fuel to the map to see if that was the issue, and it did not help at all. Certain that it was ignition/spark related, I replaced spark plugs(ngk iridium gapped at .22) and replaced the coil packs and wires to no avail. Also ran a smoke test for leaks, and had the throttle body shaft seal replaced..

It cruises fine below 3000 but the second you give it more throttle it cuts very hard.
The boost will only hit maybe 5psi, and the afr drops all the way rich. The only other idea I have is that the pigtail connector to the coil pack does not click in when attached to the coil pack and is a tiny bit loose. Would that be worth replacing? I've zip tied it fairly tight with no result as well.

If you have any advice on where to go from here please let met know. Thanks

 

mine did the same thing...

noticed what looked like weld marks on top of the plugs.
Looking at the springs in the coils, they were really rusty.
cleaned them up.
problem solved.