hi mate have exactly the same problem as you and im still in the process of fixing it.

i've tried new spark plugs

my old HT leads

new MAP sensor

different fuel

old Throttle body

and still does it

im going to order a new ignition coil pack and if that doesnt fix it im taking it into a garage and likely the engine will be tested and if they cant find the problem im going to get it taken out, and wont be able to drive it until i can afford to put my cosworth engine back in.

other than that i think one of many sensors that records temperatures is knackered.