i would not replace the stock fan with an electric. the charging system is taxied as it is and you will not come close to an adequate replacement for a properly functioning stock fan and fanclutch. as for the exhaust some have gone to a single cat but keep in mind that you need to have both O2 sensors mounted correctly or the computer will be incorrectly firing the injectors, and preformance will go down.
Is your fj62 stock or is it lifted on larger tires. because 9 mpg on a stock cruiser is not good. i get 10-12 around town on mine running on 34"s. vacuum leaks could cause this but a full tune up via the Factory service manual will point out where the loss of gas milage is coming from. if your engine has been tweaked with by someone not adhering to the FSM specs this could be our low mpg as well. things like the Throttle Positioning Sensor (TPS) need to be on, timing , valve clearance spark plug gap.
and from been there done that if you do get a new exhaus tmake it as strait as you can you can get inexpesive stainlesscats from summit racing and you will need 2 new O2 sensors to be install AFTER all welding is done on the new exhaust.
also check out the 3FE list at
3fe@yahoogroups.com even if you don't jooin the list alo of good info in the files section
HTH Jason