Hi there guys I have recently brought a impreza wrx bug eye with a mis fire on bank 4 I've changed coilpack and it no longer comes up with cel light but it still coughs n splitters under load but if I increase power lightly it's ok but if I go for boost on full load it seems to cough n splutter then eventually go on to boost I've cleaned the maf which was minging and the boost solinoid with brake cleaner and it seems to tick over better n run better on a steady drive but if you go fir full boost the misfire seems to come back I've ordered new plugs and put injector cleaner through the system but wondering what else could cause my problems

 

The car is standard other than centre n back exhaust n lowered

 

I would lean towards new plugs mate, when the plugs come try them, do you know when the last plugs were changed

 

The car had an engine change 10,000 ago n he said I had a full service at engine change but I'm also thinking they not gapped the plugs n just fitted them as they came in the box I'm gonna fit some pfr7b platinum plugs gapped to 0.7 along with a k&n pannel filter new fuel filter oil filter n oil in the next week start at basics with a good service

 

You may have a small air leak in one of the vac hoses

 

Mine has similar (2001 UK300 Bug WRX) I found a couple of vac hoses had small cracks in them due to location around/near the turbo. Replaced with Silicone top prevent future problems. Solved it for then but start to do it again, this time it's the up pipe lower gasket. As has been said, check all hoses and pipes, could be something that simple