96 Z34 Multiple/Random Misfire and exessive gas consumption

I have a 96 monte carlo z34, and am having the same problem as most people with the 3.4 liter engine. I am getting a multiple/random misfires code and a downstream O2 sensor inactivity code, and today it took a quarter tank of gas to go 40 miles. Before today there has been a gas smell coming from the engine when the car is running.
Things I've replaced:
MAS sensor
TPS
Spark plugs and wires

I've checked the ignition coil and they're fine.
I need help ASAP, with gas prices the way they are I can't afford to refill everyday. Please, anything.

Also when it idles it revs up and down constantly and wants to stall when shifting into drive or reverse.

Follow up: I just checked the EGR and it appears to be in working condition. If anyone has any ideas PLEASE HELP.

Follow up: I just checked the EGR and it appears to be in working condition. If anyone has any ideas PLEASE HELP.

Wish I could tell you, but i am having the same problems with my daughters car. She has a 95 z34, and its sucking the gas, and i have replaced the egr, could not get to the os2 sensors, but it seems to be common with these motors. I had the rich gas smell, almost like a leak, but never found one :screwy: . If you get any good info please pass it on,and I will do the same. Had a cooling problem, kept overheating, so i changed the thermostat, and it took forever to get the air out of the system.
It wants to rev high coming out of first gear, then once it shifts it has no more take off. It will not climb a hill very well. Not sure if your having the same problems.