Troubles with my GZ's engine, please assist.

[bergreen]

Hey guys, I'm new to this forum. Guess I'll start off with a bit of introduction. My name is Daniel and I've owned my 2008 GZ250 for 6-8 months now. She's my daily commuter (30 miles a day or so) and has taken me on a few road trips that average 300 miles round-trip. Kinda hard on this little motor. She has about 8,000 miles, regular oil/filter changes, clean and lube the chain, wash the bike, etc. I usually use mid-grade gas, and always give her Suzuki performance 4 10W40 oil as suggested. I just replaced the spark plug a couple days ago.

Now on to the issues. I got in a minor wreck over Christmas vacation. Some guy in a truck went very far out of his way to make sure I hit him, but that's an entirely different story. Hit his bed with my left handlebar and dropped it on the right side. No tilt sensor - brilliant - so the bike kept running. I had her standing up again in less than 10 seconds, so I don't think there was much damage as far as having the bike running while sideways. Brake pedal was bent, fender/tank/muffler scratched, front right blinker mount got bent. That's about the extent of the cosmetic damage.

Here's the engine trouble. I'm not sure if it is related to the wreck, but I figured I would include that story just in case. I will list out the problems in bullet form.

1) High-pitched whiny sound from the engine while at cruising speeds.
2) Feels off-balanced in the back.
3) Front forks and steering column are not perpendicular to the frame.
4) Backfiring out the intake/airbox when cold (probably needs a valve adjustment).
5) Slipped the clutch, hearing a metal-on-metal sound from that side, cannot recreate the sound now.
6) Noticed a small leak from the front-right of the base gasket.

Any ideas?