Is there a step down stud replacement for intake manifolds? I have a stripped one and it's a problem.

Pull the stud and install a new one.

New metric studs are less then $2.00 at McMaster Carr.

Zach

Let me rephrase that.... The hole in the head where the stud goes is stripped.

Have to install a thread insert or helli coil

I can't use a step down stud like I did with the exhaust?

Yes. You will still need to bore out the head and retap it for the stud that you want. A hellicoil or timecert will allow you to use the same sized stud.

When looking for things like studs, I have ALWAYS been able to find what I wanted at McMaster Carr.

Zach

My preference is to repair what was damaged. In this case the head is damaged and a timesert (also my preference) will repair the head and you can reuse the original stud if it is not damaged.
I have had heilicoils come loose from head/block/whatever and become stuck on the bolt or stud. Then I had a nut or bolt head on one side of a part and a heilicoil the would not fit thru the bolt hole, made for a though removal. I think it was a bolt but if it had been a rusted nut on a stepped stud it would have been pretty tough.
Note on timeserts, when installed the installation tool expands the last thread or so to creat an inteference fit to keep it from coming loose. Also since it is solid not a coil you can put locktite on it if you want/need.
No, I don't sell Timeserts but I do like/use them.

Jim