2 bottles of Chevron Techron Fuel system cleaner (1 bottle treats 10 gallons). This is a great product...and very easy to find. I would do 2-3 tanks as you have been advised.
Not all fuel system cleaners are the same...and this one seems to be highly recommended and very easy to find.
It is best on an ongoing basis to do a good treatment about 3 times a year...
The cleaner does a good job.
How old are your spark plugs?
The need to be Double Platinum spark plugs.... and those are only offered under the Motorcraft and Autolite names.
Spark plug wires?
Air filter?
There are several things that can cause the clunk sound in the front end...... 1 is where the front of the front suspension connects to the subframe.....
If look under the front of the car....right under the oil filter is the one on the passenger side. You will see a rod...that goes through the subframe....with a big nut on it...... At that nut...in the subframe is a bushing. The mount for the bushing can break free.....and move slightly...causing the clunk. The solution is to have the subframe bushing mount welded. I have a picture of this location in my pictures at
http://community.webshots.com/album/201931518cScpNK
It is not something that is going to fall out....just make an anoying sound....the movement is VERY slight....just enough to make a sound.
Another cause of the clunk can be caused by the subframe bushings....These are at the 4 points that the front subframe connects to the unibody.
Put simply.... The front suspension is connected at several points to the subframe. The subframe is connected at 4 points to the unibody of the car.
I also have the fuel filter shown in my pictures.
Please take note that the intake on your '95 is MUCH different than what is on my '96...and later years.
The lean code for bank 2 sensor 1 is most likely caused by a vaccum leak. If it comes back....hold off on the auto parts store advise to replace the oxygen sensor for $50 or more....as that rarely solves the problem. If you have the 2 catalytic converters as the '96 and later years have.....then you would want to replace the oxygen sensors in pairs....as the switching charactoristics slow down over time. The PCM will light up...and there are specific codes for oxygen sensor failures......including a specific code for slow switching....should the switching become too slow.
My point in replacing the sensors before each converter as a pair.....is that you want the same switching charactoristics for both banks of cylinders.