Misfires on Decel

[boomtime]

Normally I am not the type to post up problems without trying to figure it out. When I fix Audi's I prefer to work thru it with process of elimination first.
This problem I have been chasing for almost a month.
Whats happening is on deceleration, im logging misfires between 1600rpm and 2200 rpms. Almost no issue as idle, slight rumble.

Its hard to notice the issue with the music playing, on deceleration or cruise control climbing or leveling off its sorta like a stutter or shaking for a few seconds. Later I also noticed a random popping sound when the boost hits above 15psi but no loss of power on high boost or WOT. It could be knocking/detonation but maybe fuel exploding in the exhaust?
I swapped plugs, coils but misfires stay on cylinder 4. Replaced plugs with the colder 8 ngk iridium but the problem still occurs.

Starting to think injector 4 must be leaking and maybe the tune doesn't mind the extra fuel???

[boomtime]

Good news, my hunch was right it turned out to a bad seal on injector #4.
After I posted up, I ordered 4 new Bosch injectors, injector seals and manifold seals.
I continued to drive to work daily last week and the problem started to get much worse.

Ultimately throwing codes P0300, P0301, P0302, P0303, P0304. Basically now saying ALL cylinders misfiring.
I did some vcds logging on misfires to discover it was still really cylinder #4 with by far the most misfires. The other misfires were likely the result of #4 dragging the engine down.
Normally on Audi’s this is usually ignition coils, plugs or compression problems, either carbon, bad rings or bent valves.

HOWEVER
I pulled the intake manifold and fuel rail to find the #4 injector felt loose and visibly scorched, probably due to combustion gases leaking past it, which caused the popping sound I was hearing at higher boost levels. You can see the missing seal on #4 in the pic.

I cleaned the injector wells, vacuumed out each cylinder just in case some debris fell in when pulling the injectors out. Slapped 4 shiny new injectors in. Torqued it all back together and boom, no more misfires, codes and the car is running VERY strong again!

I know this will help someone someday, here are some pics!

[GIACuser]

Thanks for posting both problem and solution. How many miles did you have on the car and how long have you been running e85?