Bent up stuff

The "running rough" is your first sign of bad timing. What your buddy did aside. Lets start with some more specs.

Give us full motor details. As much as possible. Including mileage, any passes, highest rev (that you know of) and what not. Increasing timing increases possibility of many things. Including detonation and such. What do your plugs look like? Have you pulled anything else out of there?

EDIT: Don't let your buddy touch your engines anymore.