Metra cab car question

What kind of horn do the Metra cab cars have?

All kinds. Country and Western.

The current series of cab cars are the 8400-8413 built by Morrison-Knudsen in 1994-1995, followed by 8414-8478 built by Amerail between 1995-1998, then followed up in 2002-2005 by 8501-8608. The 8400's were spec'd with Nathan Airchime K5LA horns which have all but been replaced with newer K3LA horns as their rebuilds progress further along. The 8500 series cabs have K3LA horns. The older 8200 series cab cars can still be seen in regular service as coaches but with Nathan P5 and Leslie RS2M horns still attached to them.

There were also Westinghouse AA-2s. The old Pullman cab cars had them, and they were apparently put on newer cab cars from time to time. This is the same horn that certain cars on South Shore, North Shore, and briefly Chicago Aurora and Elgin used.

Which horns was Metra modifying for overhead clearance, by taking off some of the trumpet ends?

If I recall, the AA2 was the norm on CSS orange cars. Throughout the 80's, they would pop up from time to time on the new cars, but none remain that I'm aware of. It seemed like the horns on the westbound ends of the cars were that weird single-tone Japanese horn and the east end were the AA2's, it's a pattern I remember quite well. Today all cars have P3 if I recall right. It made me feel at home when I lived in Kansas City and some ex-CNW power on UP came by with their P3's.