What megasquirt?
 

I have a 1990 it's a 1.6L and I bought a 1.8L full turbo a few months ago I'm just wondering which megasyringe I should use I was told to use a 1.6 megasquirt, a 1.6 harness and just hook it all up for 1.8 and i should be ok, but i just wanted to test and make sure before buying a control unit for a lot of money.
Thanks

I'm just a dummy, compared to most of the members here, but my understanding is you buy the squirt that fits the car. Make your mods under the hood. If your 1.8 is vvt you definitely need MS3 and will wire that separately.

If using a PNPyou need the megasquirt for your chassis.

You can wire the VVT bits with the options connector.

if you get a wire yourself unit, or a PNP -either way you’re going to want a MS3 based unit. No question