loss of power

hi fellas any help on this one or has anyone had it b4 ?..............................got a 3.9efiv8 classic started to lose all power when accelerating then cuts out but when you start it up again runs sweet as a whistle press acceleretor agin it dies any help plz could this be an air leak if so were should i be checking plz

I've got 3.5efi 1989. Was losing all power when accelerating a few months back. I cleaned all the earth leads, battery leads etc. in the engine bay and it was fine. Relocated a couple of the ends, especially the braided ones that are bolted to the inner wing, cleaned off the contact surface and sprayed some WD40 before re-bolting it. No idea if that's the done thing but it worked for me. Cheap to.