[Vwdiesel] Exhaust ideal and oil pan?

[Tony and Lillie]

So, it's interesting that in all the years of hotrodding, I've never seen a calculator for exhaust sizing on an engine. There are calcualtors for injector size, carb sizing, tires sizing, etc... Anyhow, this comes form my diesel 82 Jetta needing an exhaust system. I'm going to change the mainfold to the dual setup, and wondering what the ideal size is for the rest of the system. 

Do diesels opperate the same as a gas car in this theory, or is it completely different? 

The car is a 1.6 NA, BTW.

Also, I was under the car today, and I noticed there is a fitting on the back of the oil pan right above the drain plug. It is about an inch in diameter by an inch in length. Is this probably an oil pan swapped form a TD?

Tony Hoffman