Recently failed smog. I had my engine and heads rebuilt at 229000 miles. I had replaced oxygen sensor, TPS sensor, spark plugs, wires cap and rotor, catalytic converter, ignition coil, engine temp sensor, cracked exhaust manifold, radiator hoses thermostat. my mileage now is about 257000 miles.my truck had gradually started too run very rich, MPGS were very poor. @10 mpg. when I had taken it smog. my base timing was 10deg.BTDC anyways failed. so I took it to a mechanic which was recommended by a buddy of mine. after being in the shop he check top to bottom for the problem, turns out the computer was fried. after replacing the ECU it still failed. IM thinking WTF! my mechanic recommended driving it around a couple hundred miles to burn off any crap stuffed in the catalytic converter. before I smog it again