With those systems, it can be hard to say for sure. It could be a stuck compensator valve. But if it was a used pump you bought, it could have been worn when you got it. 

Does the hydraulic oil get real hot? I think all 2-105s had the hydraulic oil temperature light. Is that coming on?

Another problem that could be heat related is the relief valve. There is a body with valves in it that the high pressure line from the pump goes to. It has a couple of pressure control valves in it, and they are controlled by springs. If those springs got hot and lost their temper during the fire, they're going to open at the wrong pressure. The valve that regulates PTO pressure is in there as well, so this would explain a lot.

I believe there are specs for spring strength in the shop manual. Now would be a good time to check that out.