again here it goes. Start with the 6 P's. When you said you've replaced all the connectors, have you actually replaced the EFI harness? Corrosion is a b* and if you have any on any connector it could cause a load of problems, ask me how I know :-\. Have you done a vacuum/boost leak check? You said the car has not ran for 15 years is that AFTER the engine rebuild or before, I know it's a dumb question but you never know. Have you checked timing (part of 6 P's)? It could literally be just about anything. Starts with the 6 P's and write what you found.