I recently bought a 96 v6 car that was swapped to a 4.6 out of a 96 crown Vic, when I bought it misfired a little at idle and horribly when trying to drive/under load since then I’ve put a new maf, coil packs, plug wires and plugs, it now idles perfect but as soon as you give it any gas it stumbles and won’t hold steady rpm and misfires like crazy any ideas on what it could be or things to test?