Hi, hopefully someone can help?
Since I bought my Cosworth there has been a misfire/hesitation when on boost
To me it seems like a fueling or ignition spark problem
Because of this I don’t really drive it as I don’t want to do any damage to the engine

The spec of the car is:
91 green top 4x4 sierra sapphire Cosworth
Evolution MSD chip and anti lag system
T34/T35 turbo Mariam shaft
Full 3inch stainless exhaust
RS 500 intercooler
Group A air filter
Dark green injectors
3 bar map sensor
Amal valve still fitted
Alloy bottom pulley
Running at 24psi
Engine internals unknown, presume to be standard


So far since I got the car I have changed a few things to see if I can get rid of the problem

Rewired the coil correctly as plus and minus were on the wrong way around
Group a coil fitted
Standard breather removed, port on inlet blocked, piped to sump and rocker cover and crankcase breather with Bailey breather oil separator bottle
Fuel pump rewired – now full battery voltage 13.8v
Amal valve changed as terminal was broke and was clicking when wire was touched
3 bar map sensor changed

None of this cured the problem
The problem occurs when on boost under hard acceleration through all gears
It does the same with anti lag switched on
The car idles and drives normal with easy driving and using light acceleration the car will boost up ok
But if I floor it its like turning off the ignition or cutting the fuel it holds back and chugs all at about 3000rpm and above

All suggestions welcome thanks