Random cut outs on a t25 holdsworth???????

[bongosi]

Hi everybody, I have a vw 1990 Holdsworth conversion - she'a a beaut, but she has a funny problem. Runs absolutely fine 95% of the time and then randomly loses power - sounds like she is not turning over properly and when you press the gas she cuts out. Then after a few hours or overnight - she starts up with no problem again. The fuel injection electronic controller has been changed and the problem persists.
Has anyone had this kind of problem before please? I am really stuck as I need to sell it and want to fix it first.
thanks a lot.......