Evening Martin,

What scanner were you using and what protocol were you using ie: EOBD or GM? On vehicles with flat spots, I normally turn my attention to the MAF after conducting basic checks. Do you have access to Pico-scope or similar which easily shows up MAF faults? What are exhaust emissions like at normal and fast idle? If the MAF is ok (assuming it does not have a MAP sensor) then you will need to check out the TPS. One test for a faulty MAF is to disconnect the multi-pin plug and see how it goes. Best of luck.

Regards

Pete M