New Member: 1995.5 Issues with 4WD and Suspension\Steering

I purchased my 1995.5 4cyl 4WD single cab about 8 months ago. This is my first Toyota and first truck (all cars before this). Truck was owned by an older gentleman and is in really good condition (zero rust etc). I have a few issues I would like to resolve though and I hope this forum can help me.

1) Rough idle only when warm (searching this appears that it might be normal). Idle stays rock solid and doesn't hunt around but I get a decent shake through the steering wheel when at red lights etc. Is this normal?

2) Owners son sold me the car so he couldn't find the receipts for service. I can tell things like the plugs, wires, cap, hoses, etc have all been replaced (new stickers etc). I had to put a new cat on it just after the purchase (CEL). Any issues with me swapping to synthetic oil in this engine if he has been running mineral? I don't know what's in there now. No current oil leaks.

3) If I drive over 50 mph the truck hunts around the road a lot. I believe all of the suspension is original. I would like to tighten it up if possible. Should I start with the steering rack bushings?

4) If I put the truck into 4WD I have drive in 4H but nothing in 4L. I don't have the ability to raise all 4 tires off the ground to see what's actually engaged. I can't find any posts on why I would loose all drive (like being in neutral) when in 4L. I don't have manual hubs.

Thank you all for the help!
- Bill

 

Is there a better place to ask these questions on a 1st gen. Tacoma?

Any help is appreciated. Thanks!