With the older systems (like mine) hooking up the laptop is pretty important to get a good tune. A wide band sensor also. I am pretty sure any newer kit comes with wideband (or should!). Also sealed manifolds. After I ditched gaskets and used a little high temp RTV I did not have any more header leaks.

You can get adapters to run the serial port into a USB. They are a bit if a PITA to get set up but seem to work OK thereafter.

If you want EFI you really need the wideband either added to what you already have or part of a new kit.

If not messing with matching up a computer is high on the list, sounds like it is either new self tuning kit or carb.