You talk about power and clutch in the same post makes me ask.. is the power loss because your clutch is slipping?? if so, there's nothing you can add to your engine oil to assist a slipping clutch. I know most of you are laughing at this, but I start with simple and work my way into complicated. can't go straight into complicated cause skipping the simple makes the complicated even more complicated. lol. so anyway
power loss. check engine light? yea? check it!! no? hmm.. these aren't very powerful (135hp crank aprox) to begin with.. plugs, wires, oil change, clean air filter? check make sure you don't have a rat nest in your air assembly. it happens!! There are ways to check for clogged cat. general methods you can google up. I gutted the 2nd Cat in my rig long time ago. I have an '01 so I have the exhaust that has two cats. the 2nd cat can be gutted without interfering with the computer. just as long as there is no 02 sensor after the Cat you gut, then the ECU has no way of knowing.
HERE'S A THOUGHT!! Power loss can occur without a CEL (check engine light) if your timing belt has jumped a tooth or if your crank timing sprocket has broke the keyway and shifted out of time a little. I seen this personally on someone's sportage. Someone had done the timing belt on their rig before they bought it and they didn't tighten the crank sprocket enough and it worked loose but just a little at first over the course of 2 months! She lost power and it had trouble getting up to hwy speed on flat ground. Then one day it let loose and the crank pulley pretty much fell off and the engine died.
I think you can pull the timing belt cover off and get a peek at the timing marks on the intake and exhaust cam gears. there's a mark on each (I and E). the crank pulley has a mark on it too.. the cam gears should be at 12 o clock while the crank mark should be within the marks.. you'll see what i mean. will need a flashlight, and a 10mm socket/ratchet (preferably a 1/4" drive). To turn the crank pulley over you'll need a larger socket.. I think it's a 22mm. But it will have to be a 12 point since the bolt on the crank is also 12point. Can't use a 6pt. the crank bolt is a 22mm I believe. maybe 24mm. ok i've said enough.. lol.