[cyruscat]

New to me 2007 Z4 / E85 / N52 with a problem.
Car has 101,000 miles and looks to never been tinkered with.

Problem is a poor idle and throwing codes for misfires on random cylinders.
Some times #2 then # 5. Can hear in exhaust a DUH-DUH of misfires.
Seems to smooth out over 3000 RPM but maybe just hidden by RPM.

OK since it is high mileage car I performed the following services.
New recommended NGK plugs
New Bosch coils, all 6
New Vanos
New air filter
New PVC/CCV
New BMW MAF, kind of pricey!!
New BMW MAP, kind of pricey!!
New serpentine belt
Flushed radiator and new coolant
Oil and filter change
Cleaned throttle body inside.
Ran fuel system cleaners until top of pistons are clean when looking into plug holes.
Tightened all intake bolts and checked vacuum lines.
Inspected intake air pipe and fittings after MAF sensor, all sealed.
Still has problem so did smoke test to look for vacuum leak. Took throttle body off and taped intake closed.

Only possible leak is behind throttle body mounting flange. Getting small wisp like a crack. Going to reseal opening and try again.

Frustrated as you can imagine.

Any ideas?????