bogs down

2014 Kubota, I cleaned fuel tank, changed fuel filter, changed air filter, replaced fuel pump, added new diesel fuel (just a little to test), I am baffled at why this is happening, but I am positive someone else will know. I appreciate any suggestions, thanks in advance. It does it at idle...

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...