1.8 could very well be the way to go, I'm not sure. I'm not willing to give up my Torsen to find out.

The early 1.6 cars had none of the bracing that started apearing in 1992. The 1994 cars (first year of the 1. had all of the bracing installed. It doesn't add up to much, but that's part of it. The 1.6 diff is also something like 15 pounds lighter from what I've heard, in addition to the engine block/head being a bit ligher. The quote I read today from Andy Hollis (a knowledgable Miata autocrosser) said the difference was about 125 pounds total.