rf interference is a big issue on knock sensor erst ecu's
there are also different types of s2 knocksensor ecu's
fitting a non knock sensor early ecu cures the problem.The knock sensor stratergy can go hay wire and takes 11 degrees out of the current ignition load site .
The erst knock sensor ecu has no default stratergy for knock sensor issues so 11 degree's comes out ,this is ok on part throttle light load situations as the ignition timing can be as high as 50 degrees advanced at this point.But at 10 psi the ignition timing is typicaly 10 degrees of advance and the engine does not like 11 degrees taking out.
The knock sensor can be removed and wrapped and tied away from the engine you can also install a 47 k resistor and throw the knock sensor away .
Cosworths don't really have these issues better ecu better maps better default stratergies.