Flexplate?

I had my differential replaced at the local amco, and they stuck what looked like a household pvc pipe fitting on top of the differential to replace an air hose connector from the intake. They didn't notice that it was too tall and directly interfered with the throttle pulleys. I noticed that there almost seemed to be a governor on the car after I got it back, cause it just wouldn't really kick in to the high end of the throttle. Then about a week or two later I was missing an exit and punched it, it stuck, full throttle. I couldn't immediately tell where the throttle was catching, (I've had my floormats stick it in the past), so I ended up starting it a couple times to see if I had found the cause while it was still stuck. As an apparent result of being started at full throttle, every time I start it, it sounds like the starter is skipping teeth on the flywheel. I took it back to amco and they checked out the starter and the teeth on the flywheel and such, and told me that there is a "flexplate" between the engine and transmission that the starter mounts to, and this has been warped. Since then the car has started making more even scarier noises at high throttle, and now even at low speeds, so I've parked it.

I can't find any flexplate in my manual or online parts suppliers, and I'd like to have a pretty solid idea of whats going on, and what sort of collateral damage could be associated, before I take it back there and entrust them with my vehicle again. Help?