24vsapphire

hi im wondering if anyone can help me???
i got a 24v cossie engine in my saph it been runnin lovely for the past 3/4 years but lately the car will only stand still idiling for approx 4/5 mins before starting 2 cut out 2 the point that u cant even rev it on the accelerator ive changed leads plugs air flow meter crank sensor swapped the idle control vavle for another one checked all the vacum hoses all wires the lot and it still playin up no matter if i have drove it all day or start it from cold it will not sit an idle for more than 4/5 mins before struggling and cuttin out. im really comin 2 the end ov my patients with it so any ideas or help would be much appreciated cheers richard