OK.
The story so far..........

Put a 89 rwd saff engine in sssc stylus kit and added 330 kit.

all was sweet for a year and then it started suffering from an occasional missfire on right hand bends on track( which i thought was fuel starvation cos it was only in rights). then it started to happen occasionaly at any time and felt like it was firing on only two cylinders. There was no pattern anymore - just where and when it felt like it.

Started it after a winter lay off and it fired straight into action ready to scare the pants of superbikes for another summer. Next day it needed turning over a couple of times to start - next day it needed turning over loads - next day it wouldnt start.

I have disconnected the coil lead from the distributer and have been observing the sparking:

Turn on ignition and a weak spark. Turn engine over and 1 sometimes 2 good strong sparkes then nothing appart from an occasional very weak spark but this is very rare.

Took injecters out and only 2 and 4 are working.

I have changed the following so far.....

Coil
Amplifier
ECU (but not chip)
ECU relay
had crank sensor checked
phase sensor
rotor arm
dizzy cap
leads are ford appart from coil to dist which is unipart

Matt recommended checking earths on inlet manifold which i did today.

Does anybody have any idea what to check next?

Advanced thanks.