2 year old steering problem...help!

I bought my '01 Aurora over 2 years ago (used of course). On my way home from the dealer, I noticed that the front end wandered at times. The next day they re-lubed the steering shaft. It helped a little bit, but then the problem came back, but not all the time, and not always to the same degree. Over time, I also notice that when in motion and coasting, if I stepped on the accelerator, it felt as if a motor mount was bad. It would feel something similar to a tranny bump. This would not always occur. Since then, and not all at once, I have had the following items replaced and in the following order: new steering position sensor, new right strut bearing, new front motor mount, new steering rack, removed and replaced original control arms and struts (found no apparent damage or worn bushings), new tires, new front motor mount + rear trans mount, new right motor mount + left trans mount. After the recent replacement of the four mounts, I realized how much the engine jumped around in that tight little space. Before, I could simple push back on the top of the front tire with my foot and watch the engine literally jump out of the engine bay. The mount replacement also improved things overall with the front end wandering and the transmission bump. But after three weeks of the last two mount replacements, there is still some iritating wandering, although it is much more tight than before. Also, at highway speeds of 60 to 70, the steering wheel shakes, and I thought I could see the tach shake a little after I let off the gas at around 65. The final issue is that some mornings when I put it in reverse to back out of the garage, it feels as if the transmission just dropped out of the car...ok, maybe not that bad, but it is a very harsh jolt that only happens when its cold. I've had several service centers check for tranny codes, but none were present. The problem just seems mechanical in nature...like a worn mount or bushing, but where I don't know. Oh, and some other conditions include the following: when in third gear the car sometimes veers to the left when I let off the gas and to the right when I accelerate (like theres more resistance without the overdrive), sometimes when I stop the car feels like its bouncing forwards and backwards slightly.

I'm at my final breaking point for this car. I've kept it mostly because the resale value sucks, and because I don't like to lose. Any help would be GREATLY appreciated.