Mc2 misfiring

[Dag Bøsterud]

I've had some problems with my 1990 Audi 100 TQ (MC2-engine) misfiring.
I thought I had solved the problem when I found a ruptured hose and a broken hose clamp, but no.
I then discovered the car running very lean, so I disconnected the OXS and adjusted the CO%.

The car pulls very good at 0,6 bar all the way through the entire rpm range now in all gears.

I switched for a stiffer WG-spring, and the car started to misfire again. Not as bad as before, but
I could feel the that something was happening. It's not like a kangaroo anymore, but I can feel that it's
small misfires.
The car is probably leaning out.

The fuel pump is brand new, I've replaced the OXS (one year ago), I've replaced all sensors except for the
air temp sensor and hall sensor, I've replaced like ten metres of rubber hose (!!) using new hose clamps...

The car has an ECU with a chip from MTM.

I get no fault codes.

Could there be something wrong with the ECU or chip?
Could there be something wrong with the fuel metering device, so the that it can't adjust to more or less fuel like the OXS and ECU would like it to?

Any help would be greatly appreciated.

/Dag
1990 Audi 100 TQ Sport Exklusiv