1985 chrysler new yorker turbo not working

My dad has a '85 New Yorker. He doesn't drive it very much but lately he complained that it lacked power. I took it for a spin and it was extremely sluggish. I could hardly get it to go over 35 mph. It also seems that the turbo is not engaging.

Any suggestions on where to start? I can get more information about the car.

Thanks!

A plugged cat converter or a broken muffler can do that. separate the exhaust before the cat as a test and see how it performs. If thats it you will notice a difference quickly so no need to go much farther than the driveway.