seriously a muffler has no part in fuel economy AT ALL!!!!
look else where to solve you problem

I cleaned the TB with it on because I had to order a TB gasket. I also changed my air intake set and tomorrow morning I'm going to cleam my vac system out and see how it drives tomorrow.

Edit: If this doesn't work then I'll look into getting another FPR or fuel pump. Wasn't there a recall on the gas tanks or something? Because when I make a hard right turn the gas needle falls like a half to a quarter tank. And its always moving when I stop and go.

actually, if the calipers are not releasing, then yes they ARE a mpg problem. its more drag. more work the eng has to do to move forward = less mpg

The no-baffle 92 tank is not causing your problem.

How about we get a fuel pressure gauge on that thing instead of throwing a pump or FPR at it?

First, I am going to ask an obvious question....what brand O2 did you get? Don't say Bosch.

Second, another question...what brand spark plugs are in there? And PLEASE don't say Bosch Plats.

Ok I'm not going to seafoam because I dont have time for a possible o2 sensor, cat, and/or manifold problem (may have cracks). I have a denso o2 and NGK sparkplugs. I'm goign to have a shop deal with the greasing of the brake parts. And I'll check my fuel pressure.

Ok, now I believe something is causing drag. Its either my rear brakes, since the wheel cylinders and brakes need replaced. I also think that my parking brake doesn't engage either. My car still slows down when I let off the accelerator 50-70 mph. It feel like driving a stick shift and you're shifting down to come to a stop. OR Is this a sign of trans problem? As far as my MPG I can get like 300 miles on a full tank driving on the highway. But in the city its like 12 MPG.

Also, I believe when you all say WOT that means smashing on the gas. if so then, when I smash the gas to try and get some quick speed, it doesn't pick up any. Its like a lack of power. My take off isn't good because I can't get momentum which probably contributes to my poor mileage in the city.

What the ****, my cat is burnt . god dam. I did the brakes and knew that wasn't the problem because the car wouldn't really roll on its on, but they needed changing anyway. That punk *** o2 sensor fouled up and clogged and burnt up my cat. I don't have a vacum leak, I sprayed the rubber fittings with carb cleaner and got no response. So what is the root cause.

I've got the same fuel needle problem, no worries. It'* pretty common from what I hear. Also, my parking brake only engages when it wants to, it was a defect in our year models.

I'm actually thinking of looking to replacing my CAT, and that may solve my power/efficiency problems. If I get to it before you, I will let you know.

too bad I couldn't really feel the difference. I just put this magnaflow cat on here a month ago.