My r34 gt got the same problem. Last time when i had it checked at the mechanic (some imports experts as they said), they told me my car had ECU problem after check it with their computer (they said drive strain problems, I think) and change the spark plugs. Since it's a tiptronic non-turbo, they told me it is nearly impossible to find new ECU or aftermarket ones. They told me I have to find a half cuts or just take out the engine check light and sell it. By the way, anyone knows any trust worthy mechanics around Melbourne that can handle this job? I very appreciate if anyone let me know so I can fix my car instead of selling it. This problem is killing me for months.