I have an 84 with a 12a. Does anyone know the diameter of the stock Intermediate pipe? I measured it and got 1-7/8"OD, is this correct? This is good info to have and I can't find it anywhere!

 

I believe my old piping was 1 7/8" as well

 

Yes. Also 14 gauge. Only the downpipe from the manifold to the first cat is thickwall 11 or 10 gauge 2" OD, which winds up to roughly the same ID as the intermediate pipe. Kinda smart of Mazda, but also kinda small for power levels at anything above stock. And even then I'm thinking 2.25" 11 gauge on a stock 12A would be better.

 

Welp, I'm going with stock for now, just to get this poor thing on the road and inspected. Upgrades will come at a later date as I get money.