When i had the P75 running on the SPI loom ,just splced at the injecor end , one that splits in to the 4 ... with ORANGE topped injectors , i had to leave a vac pipe off , just to get it to Idel , and it still ideled Realy rough , when i was coming up to junctions and put my clutch in it would sometimes cut out ,,, then when i went to re start the engine it would wind over and over aond over ...,
the only way i could get it at all good ( well better) was to leave the vac pipes off the back , them all and splice the vac pipe that comes off the pressure reg ,, ,
you need to upgade your fuel pump to the 3 bar Pump , you can find these on a lot of newer cars , 16 v punto , ect...
after i upgraded to pump made it idel a little better ,,
so i bought a P75 Ecu off a Good friend , got it posted to me and lucky enough it was Decoded, so plugged it in and fired it up , Instantly it was a million times better , no lumpy idel , no misfire, took it for a spin and there was no cutting out or nothing , it seemed to pull alot better on the 75 Ecu too ,, theres a couple of MPI ecus on Ebay ... theres a Guy on FF that if you have a socketed Ecu he will Write you a chip to decode your ecu and virginise it so that means you could plug it in and run it