77 280SE will idle but no throttle..

Hi every1,

I am new to this site but have heard really good reviews about it.

I have a 77 280SE in mint condition well i thought it was in mint condition unitil 2 days ago. I have had the car for 6 yrs and havent really driven it much but every time i did it would start up first time and run perfectly.
2 days ago took car to petrol station to fill up, started perfectly run awesome then all of a sudden it stated to miss and cough then i had no throttle and then the car stopped. I tried to start it again then nothing 5 mins later it started and idled perfect but no throttle push the gas pedal and it conked out. Towed it home. half hr later car started perfect and would rev and drove perfectly. 15 mins later wont even start it tried but wont kick over.

Spoke to few people though it could be fuel pump, but it has 80pounds of pressure, injectors are clean, injector pump is working, fuel filter clean. checked fuel lines, released 1 line and had to get at least 1 ltr of fuel in 30secs got that, was told to take the warm up regulator off and replace did that no change.

unsure of where to go and what to look for now. It is urgent i have a guy that wants to purchase car once the problem is fixed... PLEASE help...

thanks keri