Good Evening TheStoffer, that vehicle is getting a few miles up no doubt, might be worth doing a compression test and considering a head overhaul and valve grind, if the timing belt hasn't been replaced that is another item that would most likely be overdue.I inagine that is the 2 litre EFI model, online atv parts,they lose a lot of sting when the compression gets down a bit.
Have you replaced the spark plugs? Be careful with the leads, they have a tendency to leave the lead connector on the plug, (good fun to remove) if there are oil puddles on the top of the spark plugs you may need to also replace the leads and insulators.I liked those machines but they were very hard on front tyres.Cheers, qldit.An exhaust leak will definetly play with your engine power. What it will do is give less bottom end, so just like you are saying no guts in 1st gear. Plus, since there is less restiction on the exhaust it will allow for more fuel to go into the engine. Plus, since you lost your bottom end power you will be push on the gass pedal more to get the same performance that you use to have.
You will notice though that you have more top end power going down the highway it would be easier to pass people and the engine will rev at a high rpm. If you were running a v8 motor you would probably not notice the effects of an exhaust leak as much as a small 4cyl engine.I suggest getting the exhaust fixed first reset the computer by unplugging the battery for 10 minutes. Start it up and go for a drive. See if there is difference after a week or so before doing anything else major. Those Toyota engines are strong and are mode for high mileage. Unless you see smoke out the back the chances of needing a rebuild is very doubtfull.