That’s what I did. I swapped in a built 1.8l, blew it to holy hell, put the original 1.6 put back in (the short nose too 
). With all the people doing the 1.8 swaps, you can get 1.6s for next to nothing all day. Torque is nice and all, but eh.
Good luck with whatever you do. If you have questions, I’ve had boost for over 4 years now, and have added boost to a few Miatas other than mine.