false codes

i have a 2000 sr5 v6 4x4 and i have replaced the spark plugs/ wires, fuel filter, timing belt, water pump, changed the oil every 4-5 thousand miles, have 33X12X50 tires with a 2" suspention lift and i it is throwing a chech engine code on the highway but not in town and i have had it scanned about 7 times and nothing comes up. also my emergency brake light just came on all the sudden and i am only getting about 15 mpg.... any insight would be helpful.

 

does the check engine light flash or stay on? misfire perhaps? something you replaced is causing this i'm guessing. check your filter, plugs/wires. who did your timing belt?