Hi martin,
Yeah your right about the ecu but my car's not a Ford Cos,it's a Vw fitted with an injection system using components off various cars.
The car runs fine when cold 'cos the relays and ecu are cold but after a few miles it starts to cut out violently and,of course,relays and ecu are frying.
I've got both types of system fitted onto my Vw,Pectel super 8 with GGR mapped chip and an ordinary L8 off a Lancia delta evo-1,i can use both.
This bloody problem is present when using both ecus.
I can't figuer it out,why doesn't the systems fuse blow?,if something was shorting out surely the ecu(s) would have both burnt out by now?.
Almost forgot,i've just finished moving the ecu and relays inside the car,above the fusebox so i'll check again if it was overheating inside the engine bay(were it was originally fitted by me three years ago..).