help?my car is missing/skipping a beat

[ponyc]

I have a 95 Gt turbo and it was one of the cleanest around for miles when i first bought it.i had to put another engine into it and i left it in a garage to get the brakes fixed for the nct i tried nearly everything with them and they kept failing.when the car was in the garage i got them to change the manifold for the turbo because it was cracked.it seems to be since that i am having problems.the car is lying up a while as i am trying to fix it and get it through the nct and sell it.when i got the car back from garage i first noticed that when driving it in high turbo when it hit 3000 revs or in around that it seemed to miss a beat or chuck for a second and go on again.once it crosses that point its grand and just goes on like normal.then when pulled up it is ticking over very low and even cuts out sometimes.it seemed to be slightly down in power too and when driving if i took my foot off accelerater the revs would drop very fast and nearly cut out.same problem stopping at crossroads.its not doing the same in low turbo and i have tried everything i can think of.the timing was checked, i de-catted it, changed turbo,took off a fuel cut defender(fcd) it seemed to sort some of the problem but car is still missing a beat.i got a diagnostic test done and it read out code 12 which listed a lot of things:crankshaft sensor,camshaft sensor short or open,distributor fault,start circuit short or open,faulty rpm signal(no RMP signal, NE and crankshaft position signal transmitted to ecu after started for 2 seconds), module fault. I have changed the following and its still no better:distributor cap, map sensor, spark plugs, ignition igniter and coil, i have the earths checked and no problems,as i was told by toyota the camshaft sensor is built into the dirstributor cap but it seems to me they are 2 sensors in it maybe 1 is for camshaft i dont know.toyota told me even when i gave chassi no. that there doesnt seem to be a camshaft sensor on the bottom of the engine or anywhere.i am going to change the fuel filter next but i am pulling hairs out of my head and seriously need help before i spend any more money on this car.does anyone know what is wrong with this car or can anyone please help me sort this out?