I know there has been loads said about this already but I'm still unsure?

If I were to use a 1.6 CVH that normally runs a single carb, would I have to change to a megajolt or could I use the existing ignition system?

I've also got a 2.0 pinto EFI same question?

Sorry for being thick.

Generally, you need Megajolt, as most Sierra carbs are electronically controlled and have a huge multiplug on them. The factory ECU controls both the carb and ignition, so you need an aftermarket system if you want to separate these concerns. Same with injection.