I own a 2004 chevy blazer 2dr 4x4 with 168k miles. There are a few questions that I have about the vehicle.

Being a perfectionist, I like to have my vehicles in top shape. When I bought the blazer, I knew I had to put money and time into it, so i started with the usual on these vehicles:
-Steering: New tie rod ends, idler arm, pitman arm
-New front bearings
-Tune-up: Spark plugs + wires, fuel filter, pcv valve, distributor cap + rotor
-Upgraded rim and tire package
-U-Joints

I've had this one nitch that has been bugging me for a while now.

When at idle, the engine jumps/skips, you can feel it in your seat. After the tune-up, it reduced it substantially, but still felt it. I then cleaned out the throttle body which reduced it even more, but still felt it. So ive been thinking fuel injector issues. I have been running fuel injector cleaner for about 4 weeks now, and im not noticing any difference. In all, I've dumped about 4 bottles in, still nothing.

Has anyone dealt with this problem on the 4.3 engine before too?
Do i continue with the fuel injector cleaner? As I see it could only make things better.
Could it be timing related? As far as I know, it has never had the timing chain replaced.
Or could it be related to the problem below...

In addition, at idle, the oil pressure when hot drops to about 10 psi, which in my mind is a no no, should be at least 20. There are no warning lights or anything. Just had the oil cooling lines replaced, as they were leaking, thinking that was attributing to the issue, but did not effect anything. I've looked online and seen replacement oil pumps that add additional volume to account for the age of the vehicle, but i know its a costly and timely job.

There are no check engine lights or codes.

Anyone have these problems too?