a 1985 gsl se that i got a good deal on this last summer is about to be road worthy, when i purchased it the guy said that he just swapped the engines to one that was suppose to be good. but he had never gotten it to start. so i gave him $500 and went on my merry way with my new RX7, should be an easy fix hopefully, i started by changing out all the fluids to new fluids and checking my spark and fuel delivery were up to date with new filters and spark plugs. then i did a quick cleaning with dex/merc3. put in new spark plugs and wires and finally got her to fire up. she smoked for a little while then after warming up the exhaust cleared up to help me on concern with compression.
but theres one problem i have with my new RX7, it idles high, but my tach isnt functioning, and it makes this aweful clanking noise that gets louder as i rev the engine. i tried driving it around the parking lot and it has no power. idles high, revs slow, no power, continuing clanking noise that increases in volume with rpm increase.

i have checked all my fuses and changed them and put more gas in it. but i ran out of time at the shop. now it only starts with started fluid and a few cranks. i believe some of that is my battery though.

 

Can't help you on the clanking noise, perhaps an idea of shooting a small video?

But when i read your story it sounds like you have some vacuumleaks and maybe the previous owner did not hook them up correctly when he swapped engines.....