Anyone who has the LM-2, knows that it is a pain for getting it to work with HPT. The voltage floats all over the place, and never stays the same. Other times it will vary with respect to lambda, creating a non-linear output that you can't correct for.
Well, there is a solution to this problem that I've been using for a while; ground the output.
This works, because with the LM-2, Innovate made the unit able to output differential signals. Due to the nature of this design, the negative side of the output is not grounded within the unit, even when ground is the reference. By correcting this externally, we get rid of the float.
When you hook up your LM-2 to the MPVI, hook it up as follows;
Pin 1 on EIO - lime green (analog1+) of LM-2
Pin 5 on EIO - yellow (analog1-) of LM-2 AND to a good ground source.
Now, what I have done on my personal unit; I opened up the power plug-in, and soldered a 22ga wire from to the ground side, and ran it to the interface. I feel this is the optimal location to ground to as the LM-2 is grounded at this source, so the output signal should be as well.... plus it's easy to disconnect.
Note, that this fix might work for other widebands that seem to be floating, as well. Make sure to verify before tying this, that the negative signal of your system can be grounded without damaging the wideband unit.