I bought an 87ish donor car, and upgraded the wiring for MAF. The car starts, runs, drives, but surges a little bit, and once it hits operating temperature, runs worse. ALso, VERY rich. Burns your eyes to be behind it. I went through the MAF checklist that others have posted for code 66.. At idle, I'm reading about 1.2ish volts.. maybe slightly under (was a couple weeks ago I took the measurement). According to that checklist, that is correct for the signal wire, and the problem must lie in the ECU? And other things to check (wire continuity is good, 12 volts is good, etc). SHOULDN'T be anything wrong with using the original harness and adding the 4 wires if it's going to an A9L I wouldn't think.