PeterC wrote "GEMS also have a history of problems with high rpm misfires which seem to be related to poor crank position sensing on the k-series. "
Really? I thought it was just mine...
Apart from some serious argy-bargy I had with their MD about them lying to me about what was included in the price (the upshot being that I ended up paying an extra 350ukp or so for stuff they told me was included), mine was always very poor at starting (I ran for nearly 2 seasons using a fan heater under the engine for early morning cold starts) plus the engine wouldn't blip cleanly from idle (no amount of map tweaking would cure these problems, even by GEMS themselves). It was assumed that these were characteristics of the engine, but when the plug-compatible M3D came along I translated my maps onto it, plugged it in, cranked it up and voila the problems were gone. I still revel in the ability to blip the throttle at idle without the engine spluttering & misfiring. GEMS did try to help, they had the car at their workshop for a week and concluded that the ECU was behaving. After I got it back it suffered from the high-rpm misfire that Peter has mentioned. No prizes for guessing which ECU I use now.
Mike