I can tell you from personal experience that all of the above suggestions are good advice!
I have had the same experience with an 8V92 and the first time it turned out to be the fuses for the injectors.
One bank firing and one not. Sounded like it was running fine at idle. But a sick dog on take off. Once up to speed it did sorta OK but still not right. Changed fuse holders no more problems. Ran bus 3 more yrs and sold it!
Second experience was coming home from NC and in the mountains it was a complete dog. On the open highway it'd make do, but still struggled with any hill, or trying to acceleration at all.
And after pulling into a rest area to check it out w/no problems found it was a dog the rest of the way home.
After calling "The Don" he told me that he was pretty sure it was a bad boost sensor. Took the old one out, got the part # off it drove to Memphis and picked up a new one took it home, installed and test drove!
Had the bad connections before too!