I have an unusual problem here which I cannot even find anyone else having the same problem.
The engine is a m117 a 330HP 10-1 comp. 560
It has two new fuel pumps, a new fuel tank and acumulator. New flex lines to the fuel head. new hard lines.
A new rheostat,
I had to replace the 8 pin ignition for a 4 pin type from a 420 because I couldn't find another 8 pin unit .
Injectors tested perfect.
new heat sensors .It has a air temp sensor in the intake snorkel.Unlike US versions.
new plugs and leads. Rotor and cap are new .
So all of the normal stuff has been done.
The fault
The engine starts and idles perfectly .
Open the throttle above idle and it back fires through the exhaust ,running as though a lead is crossed (new leads and plugs !) but above slight throttle it suddenly runs clean and revs perfectly. It only misfires like this at the same throttle position ,not at idle,or at full throttle. As this is the normal throttle position in town driving , it makes it undriveable . it doesn't appear to be running too lean as suggested in the WSM as it is actually a bit on the rich side.
Any ideas?