My buddy has a 1994 GT 5.0 HO and they did away with the cats and stuck simulators on it. Now I thought Simulators were for after the cats using before is pointless and couldn't it sent the wrong signal to the ecm. See the problem he's having is hard starts especially cold. But after a min it straightened out then after about 15 to 20 min of driving it stalls and sometimes it can only be driven with od off or it stalls and is hard to get started again. But after a while will start. Please help