B21 Bogs down for no apparent reason

[ImConfused666]

I have a 1999 B21 that was abused by it's previous owner. It runs great in a straight line. When I turn hard to the left or the right, it starts blowing black smoke and bogs down. That means it's acting like it's under a heavy load. I've also noticed that if I start moving the bucket up and down when it starts doing that, then it starts to run right but only as long as I'm moving the bucket. This makes me think that the problem could somehow be in the hydraulics...

I'm totally confused.