I've just finished tapping the 1/4" NPT tapered hole for the brass 90* fitting I'll use on my eralier IM for installation into my 96 A4. If your manifold has the correct provision for the year/model you plan on installing it on then this step is unnecessary.

To remove the old fitting just grab it with vise grips or channel locks firmly and twist back & forth while pulling it outwards.

The remaining hole has no need to be drilled to size as it's the perfect I.D. for tapping as-is.

Tapping this hole is going to give you a great idea just how hard nickel aluminum is. While there'snothing complex about this procedure it does take some 'grunt' put into it. Use a tap wrench as they're cheap and don't try to do this with just anything that will drive the square shank on the bottom of the tap. If you start this tap off-center or at an angle you'll never be able to tap deep enough and it'll look like luke-warm ca-ca protruding from the font of your IM as it's very visible when you raise your hood.

The other thing to be aware of is to tap ALL THE WAY TO THE FINAL THREAD ON THE TAP!! This is important as it'll give the firmest support to the brass fitting going in there with minimal (if any) exposed threads showing. Once the hose is slipped over the barbed fitting going in there it will appear absolutely stock.

IM Workshop postings are going to start re-appearing now as I find time so fetch and keep any pics I've posted recently in my pic poster that you may want. The IMW postings are pic-intensive and I'll need to be deleting as I add new stuff.

PS; the crescent wrench in the lower right was NOT used to tap. I only used it to back the tap out a couple turns so the size of tap could be seen in pic. If you try using an adjustable wrench for actual tapping you're setting yourself up to ruin your manifold or a crappy/crooked tapping job.