D-Jet lean theories Options

[Morrie]

Hi Guys,

When I did a recent tune up on my car's EFI I noticed a few interesting things. Most importantly, the car is running strong, but lean. Here are my observations and findings.

Engine is a 1976 2056 running D-Jet and a 123 Distributor.

Spark plugs were clean, but a little more white than the golden brown I would like to see. Not severely burnt, no signs of oil consumption.

Idle mixture knob on ECU is full CCW to idle. Still surges a little like it is running slightly lean still.

AAR tests good. Correct PN. Closes securely within 5 minutes.
All new vacuum lines, all lines have clamps.
CHT sensor checked. Passes resistance mesurement checks both warm and cold.
MPS holds vacuum for 15minutes (Decided that was good enough and terminated test).
Checked and adjusted FPR. Now set at 29psi and holds steady. Holds pressure well after shutdown. (check valve) No drop or change in pressure when engine is revved, or during starting.
Vacuum line routing checked and re-checked against 1976 requirements. Note that this means that the crankcase is vented to the air cleaner without a PCV valve, unlike the 73 and earlier models.

These are the basics of what I have checked. I have not gone aheaad and checked flow on injectors, though it is on my list of open items.

Today I pulled the MPS to check the part number. It is the correct part number for a 2.0, but not for a 74-75. Its the proper part for a 73 2.0. Since the 73 2.0 has a different vacuum system, more of a closed circuit with the crankcase, I am theorizing that this sensor is expecting to see higher pressure numbers than the later system, and could be causing it to instruct the computer to operate at more of a lean condition.

Any thoughts from those with more experience than I would be great. I am climbing the learning curve here, and am way past clueless and now at the stage where I know enough to be dangerous.

Thanks in advance!!