Have you troubleshooted the A/F ratio at all? The Bosch ignition systems are kind of a pain to do this -- I know at idle you can measure the duty cycle using a multimeter. I imagine if you ran longer wires you can get it into the passenger compartment pretty easily, but keep in mind it will fluctuate under load. I would also make sure that the MAP plate depresses and returns to its rest position without binding or resistance (it requires a little bit, but should be even throughout its depression). I would not think ignition is the issue unless it is clearly misfiring.

One other thing to consider is that the M103 is not a powerful engine by todays standards, and relies pretty heavily on gearing to get it going (esp. the 2.6). I would make sure the trans is kicking down correctly in addition to troubleshooting the AFR.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth