I was installing new headers on my 02 f4i, and I snapped one of the exhaust studs in half. Does anyone know what pitch and thread they are, or a link to buy more?

 

Welcome to the forum, what a pain that is.
https://www.partzilla.com/product/ho...05bd0dae76ccf8
8x24, remember that the diameter is smaller on the stud end.
Lets see some pics of our ride.

 

Here's my ride, ordered some new studs and nuts. Now I just need to find some bolt extractors and hope for the best

 

Very, very nice. Fingers crossed with the studs.
If there is a little stump left I have managed with cutting a slot and using an impact driver on my old F3

 

I'm having some trouble getting the radiator off, any tips? Do I need to take the headlight cowl off?

 

There are 3 bolts holding it on, two at the top and one in the middle at the bottom as per the attached:
https://www.partzilla.com/catalog/ho...radiator-01-06
You should be able to tilt it out of the way with just removing the lower bolt if that gives you enough access. The cowl does not have to be removed.