Won't rev from idle to 2200rpm

[Dr Rock]

'85 16s: starts fine and runs fine, turbo great, all for the first 15 minutes. After about 15 minutes if you come to a stop at a junction say, the car idles fine, but as soon as you put your foot on the accelerator it won't rev. Take foot off accelerator and put it down again and it will rev, but it won't hold a load unless you keep the revs above 2200 and slip the clutch.

AMM resistance is 380 ohms and can be changed, car has '86 ECU in kickpanel (missing when rescued from breakers), good spark at all plugs, plugs are NGK and new, vacuum hoses have been checked and replaced, coil is good. NTC is fine as well and no check engine light comes on. No O2 sensor or catalytic convertor on car.

Anyone got any ideas as to what is going on, 'cos I am running out of ideas?

Cheers,

Fraser