I have a 1978 mustang II Hatchback, 2.3 liter, 4cyl engine, identical to yours here, but we are restoring her now so she looks a little rough and sounds it. When I first got it there was a single barrel carb, wired onto the intake, with 1 open port, but it ran, some old lady had it. I pulled that off, put a nice little motorcraft 2 barrel on, the correct one for that year model and it started backfiring out of the carb, pulled the valve cover off and the 2nd to last valve had a thrown rocker arm, I replaced those, and cleaned everything off, and tuned it all to specs. The engine runs great in park, I can leave it sitting at 2500 rpms, as long as I want to, longest I have just let it sit an run is about an hour, maybe 2. no problems, same with just idleing. But I cant get it to idle much below 1200, Every port on my carb is capped at the moment, because I have around 10 hoses, that I need to replace and some I need to find. because none of them were conencted to anything else on the entire engine when I got it, and I cant find a good hose diagram anywhere for it. Any help on getting this thing running good, and tips on upgrades, wanted to make this a mini-stock, but seems like for the same price to get maybe 150-170 hp out of one of these eninges, I can put an 6 or 8 cyl in and get cheaper easier to find parts, and way more power. But since I have already dumped 400-500 on this engine I dont want to just pull it and start over.