Hi Jim,

Long time no see! Hows things? I assume you're away again?

I can only really answer one of those questions............the 4x4 Mahle is slightly lower compression than a 2wd one, it has more of a bowl in them. When used in conjunction with a std 2wd(only 1 light precautionary skim done in it's life) it lowered my c/r to just over 7.7:1

HTH's

Cheers,
Ian