1994 Chevy Silverado C3500 Diesel 4x4 Dually - Wastegate Solenoid Issue
 

I'm trying to locate my wastegate solenoid. My truck is thrown a DTC 78, which is supposed to be the Turbocharger Wastegate Solenoid, indicating a need to replace. I can get one for like $50- but I have no idea where its located.

My problem is that when I get around 40-45 and 55-60 MPH my MIL/SES light comes on, then goes off. When I plug a paperclip into the ALDL under the steering column and check the flashes, it gives me a 78 (7 flashes, a pause, then 8 flashes, repeated 3 times).

Where is this piece located so that I can replace it?
Also, are there any other wastegate related parts that I might/should replace?

Look around the exhuast