Not running right.....

I have just put a new maxpeedingrods turbo on my 1997 940 b230 and its not running right. I've welded in an aem afr sensor and loosely connected to see whats up. When started it idle at 10 as warms up goes to about 15. But when I rev it it bogs down to 8-9 if it doesn't cut out, it then goes all the way up to 19-20.

The car was running fine before I changed the turbo

Any ideas?

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Do a fuel pressure check and verify the fuel pressure regulator is functioning.

Maybe there is a boost leak after you changed the turbo and the MAF sensor does not see correct air flow.

It looks like a problem with the MAF in some way

I presume that the original narrowband is still installed and is controlling the ECU or are you trying to emulate a narrowband control signal using the wideband ? Using the wideband to emulate a narrow band signal does not always work so well.

How 'loosely connected'? If you are still using the narrowband for ECU control, I would look for leaks in the turbine exit pipe and also confirm that the narrow band sensor is still functioning correctly. On the compressor side, a significant air leak on the compressor inlet will cause under fueling because the MAF is under reporting engine air flow resulting in high AFR values. A significant leak on the compressor discharge will cause over fueling because the MAF is over reporting the air flowing into the engine resulting in low AFR values. However, once warmed up the engine should go into closed loop control and attempt to correct small compressor side leaks back to target AFR. It won't fix big leaks (which should be obvious). Closed loop control will not fix turbine exit pipe leaks which cause the O2 sensor to read incorrect values.

Check to make sure that the fuel pressure regulator MAP reference is still connected.