Toyota Repair: Engine performance, compression gauge, piston ring

Question
    I own a 86' 4-runner, w/220,000 miles, fuel infected, standard 5 speed. My question (problem) is when I am starting off in first gear on a grade slite or steep I have to feather the clutch to go. On level surfaces, if I want to accelerate fast the engine has to be reved. Even then acceleration is slow. Top speed is now only 65mph on level ground 70-75 on down grades fully accelerated. I can be going full out at 65 and start an incline and within a matter of minutes I will be going 25-30 mph in second gear. The engine seems to be runing fine as well as the transmission. I've looked at and adjusted everything I can. But, like a lot of things if I look to hard or long I start to miss or over look what the problem is. Can you help me? I have had to take the airintake chamber off and clean the sludge out due to a leaky intake valve. Even then this problem did not exsist. I also have taken out and cleaned the injectors. I have noticed that there is oil leaking from the exhuast manifold. Is my engine dieing?

Answer
You need to look at the basics first, the most important thing that you can check is the cylinder compression, if you do not have a compression gauge you can have it done at a local repair shop, the compression for each cylinder should be between 160-180 psi on each cylinder, if the compression is low on all cylinders there may be a piston ring problem, if the compression is low on one cylinder only it may be due to a burned valve but there should also be a noticeable engine misfire if that was the case, if the compression is good there may be a restricted exhaust system,possibly a clogged catalityc converter, you can try disconnecting the cat converter at the front and see if the problem goes away, if so, the cat converter and the muffler are clogged up because the converter disintegrated and clogged up the muffler and both will have to be replaced.