MSP Stumbles Badly at Only 1 PSI

Just started yesterday on the drive home from work. The car drives fine at low RPM but if once it starts to boost there is a terrible stumble or hesitation. The engine is STOCK except for an ATP wastegate holding 7 PSI.

I checked all the vac lines and they look ok. The car will hold 7 PSI but stumbles as though it was fuel cut.

I got a CEL finally today and it reads CYLINDER #4 MISFIRE

The car is driveable but needs to be fixed.

I don't know if this is the problem or a symptom of something else

I just started a new position earlier this month and we sold our SUV so the wife and I are down to just two cars. I cannot afford the downtime.

Any info you guys can provide would be appreciated.
 
Check the simple things first like your spark plugs for any signs of being fouled out.

How many miles does the car have?
Possible weak injector, vac leak, boost leak... there's soooo many things it could be...
 
I talked to a friend and he thinks it's the plugs (which are 1 year old). I'm debating if the misfire is due to a bad coilpack, maybe I'll switch #4 around with another cylinder and see if that one misfires too.
 
Plugs first but coil packs are a common issue I've been through 4 but more from running much higher boost I'm sure more than anything.

Also fuelcut would be very violent...like hitting a brick wall!
 
Well I swapped the coils around and drove it hard. No CEL this time but there's still a little hesitation. It's not as frequent as before but it's there. We'll see how she drives tomorrow morning when it's cooler outside, but I doubt it's a fuel cut issue.

Would a faulty BPV have these symptoms?
 
Bad corn gas? Too warm for fuel cut here now. Check the plugs and do a Seafoam treatment and put the rest in with your next fill up.
 
have you pressure tested your intake system with a pump yet? could be leaking injector o-rings, leaking IM gasket, leaking pipes etc. pump 10psi in the system and see how fast it leaks out. spray soapy water on the IM and IC piping and you will see bubbles if you are leaking. the car is 5 years old now you would be surprised what could be leaking in your intake system.
 
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