HELP! major loss of power!

[Touring240]

HELP! major loss of power! I was driving yesterday and all of sudden when I hit the gas It felt like I was on 3 cylinders or something was stuck in the exhaust.at one point I reved it to 6000 and a puff of smoke came out the back and power returned for a few minutes but then it became slow again. wtf is going on?

today after driving some more its the same thing! nearly no power.

timing chain stretching?clogged cat convertor? its the stock 91 engine with 240 kilometers on it

thanks

[Touring240]

update: just went out and felt for throttle cable slack and there was lots.I adjusted the cable using the 2 locking nuts and went for a rip. its back to normal! wtf!

throttle response is improved and if I put the foot to the floor it actually moves in a hurry now. hopefully I have fixed the problem. I'll drive it somemore this evening to see if the problem comes back