I bought a 1990 stang as a project. My intent was to hop the motor up a little and have some fun with a screaming 5.0. Since I was going down and dirty with the project I wanted to convert to carb from EFI and make everything more simple. I bought an intake and carb kit from summit, deleted the CPU, got a new 65,000-volt distributor and a new fuel pump. As I was doing stuff to the body I thought it would be a good idea to tear the motor down and put a motor freshen-up kit in it. It consisted of all new rings and bearings for the crank and gaskets. Everything went on nice and by that time I was ready to drop the motor in and get it started. It fired right up but I struggled with getting it to idle good. I thought it was maybe just the carb needing to be adjusted but I didn't have any luck with that. After finally seeing that the headers on some of the cylinders (1,2,6,8) looked completely new (not getting hot) I knew there was a problem. I took the plug wires off those cylinders while it was running and it made no difference. I put new plugs in it hoping that would fix it but it did not. I then tested compression, it had a good 150psi (10:1) in each cylinder. Then I pulled the vacuum, it had a good steady 16in at 800rpm. After seeing those components were in the clear I thought it could be the distributor. I bought a spark plug resistance tester and that proved a had good solid spark in every cylinder. Then I pulled the valve covers off and reset the lash and made sure the valves were opening and closing as they should. Everything looked fine. I'm very stumped on why some of the cylinders are dead. If anyone could point me in the right direction that would be great. Thanks, Luke.