The horn that goes from the intercooler outlet to the intake manifold is secured using 3 M7 nuts with spinning flanges. I've looked on RealOEM and don't see them. Anyone know the part number? Thanks.

Found this illustration on eBay. Is the part here? Maybe you can get a dealer's help.
https://www.ebay.com/itm/20236850453...3ABFBM0MHgublf

Wow, great find. It's part number 7. Thank you.

Check your local Ace Hardware. They often have exactly what I'm looking for -- best selection of hardware anywhere.

The diagram cooper48 linked looks like it should be on RealOEM. I'd looked in the Engine and Fuel Preparation sections with no success. They made the most sense but I went back to see if any other sections might be a possibility. None seemed right but I tried Radiator on a lark. Sure enough, it's there. I think they should rename the section but whatever. The part number is 07129905541.

I sometimes get nuts and bolts at Ace as well but I don't recall seeing nuts with spinning washers there. I'm sure I could use a plain vanilla flange nut instead but I get a little OCD about these things sometimes. Thanks again.

Yes, they will some times have them in their specialty nut assortment, it really depends on the specific store and what they ordered from their vendor.

FYI, a standard flange nut will also do the job. Basically it's just to keep the nut from backing off from vibration while doing the least amount of damage to the parts. (Like a standard lock washer can do)

Lots of online options for hardware (nuts and bolts). Much cheaper than the parts stores