An exhaust manifold replacement. I couldn't even see the oil filter bracket, let alone get it off, so I knew I would have to take the manifold off to get to it and the two oil cooler hoses. When I took the manifold off, sure enough, it came off in two pieces. That oblong shaped o'ring on the oil filter bracket was indeed the culprit. Both rings were cooked and flat as a pancake. This project went pretty well, but my arms got torn up. Gloves helped, but if I ever have to do it again, I would wrap my arms in ace bandages as well. Every part on this vehicle exists for the sole purpose of tearing your flesh to shreds. I did have to modify the heat shield a little by drilling new holes and cutting some places down. I thought about just leaving it off, but the new manifold was so ugly that I wanted to cover it up. And maybe it will be some help to keep the heat off the filter and oil cooler hoses. Just want to thank everyone here for their help in fixing this common problem. If anything like this happens to my 2000 V6 4runner, I'm going to sell it because I can't even imagine working on a motor that's shoehorned into it. I would have to think that it would be easier to just pull the motor. I'm not done yet, and I will be picking your brains for more help in the near future. Thank you all again.