Please Help ! ! ! !

I've got an 88 S-10 4x4 blazer with a 2.8L thats eating gas. I'm getting around 10 mpg and I was getting 20 mpg.

It has r-15 245 tires on it and had a recent tune up, plugs wires etc...
The cat has been hollowed out, about a year ago and I've always kept up on oil changes and tune ups.

The gas tank leaked, which I thought it was the reason for the bad gas mileage, but after fixing the leaks it still eats gas.

The EGR, O2 sensor, and thermostat have all been recently replaced, within 1.5 years.

Soo just recently:
I changed the plugs wires cap rotor, again!, the problem still exsist. so now I've been told that it could be the MAP sensor and/or the idle sensor..... not sure on this. ANY ADVICE FROM ANYONE????

I'm also currently runnin a can of seafoam through a tank of 93 octane. And a friend of mine told me to run a bottle of tranny fluid through it to clean out the motor, but this sounded kinda redneckish to me.

:banghead:SOMEONE HAS TO BE ABLE TO HELP ME ON THIS....PLEASE!!!:banghead:

You would get some replies if you put the year, make and problem in the title, rather than a just please help, as everyone doesn't read every messeage on this board. I know nothing about the 88's so I can't help there.