Running Rich problem

[captain nismo]

Hey guys. Just recently, i've noticed that my car is running rich. It is a 1989 240sx with the stock ka24e with 163,xxxkm. A few weeks ago, my gas mileage was getting bad. I asked around and some people thought it might be a bad o2 sensor. I have the FSM for my car, and i ran some diagnostics, and found out the o2 sensor was not working. I then replaced it with a new one, but still the symptoms persisted. The symptons are: bad gas mileage, back fires often during gear changes, stumbles abit on acceleration ( for example, when you slip the clutch from a standstill into first, it bogs and shakes pretty bad. You have to apply gas (approx 2000rpm) to launch normally.) Also, but these maybe unrelated symptoms: Car shakes like crazy on idle( idle is set at 800rpm), and it sounds like there is an exhaust leak somewhere under the car because it sound like a old-skool domestic/harley. Sorry for the long post, but i have quite a few things to ask;) Thanks for any help.Chris

[NISTECH]

try testing your air flow meter. 0ne 0f the wires should be 1.3 to 1.4 volts at idle, check your coolant temp connection, do a leak down check on your injectors. use a fuel gauge start the car shut the car off and imediatly pinch the fuel line between the filter and the injector rail. if the pressure drops to zero you have a leaking injector. this may isolate both your fuel milage prob as well as your idle prob. as far as exhuast look for the hole.

[captain nismo]

Thanks NISTECH. I'll check the injectors this weekend and the MAF. The procedure should be in the FSM also, correct?