go to home depot and get a little brass valve and some fittings to rig up some 5/16 hose. with old plugs in....(this can foul plugs if added to fast) bring engine to operating temp and then shove one end of hose in the can of sea foam and shove the other end of hose into your pcv hose or brake booster hose. pcv is best if you have one on the carburated model. (pcv hose will get all of the cylinders) adjust it to a slow drip and use 1/3 of the bottle, dump 1/3 into gas tank and 1/3 into motor. after you get done with the drip injection go rod around and get your cat good and hot and it will put on a big smoke show. this will help clean the cat out, intake, carb and valves. I have seen before and after emission results and this helps a lot. then adjust your carb. (no need adjusting a dirty one) a new cat might help too, there is no second 02 sensor to monitor your cat to see if it is within threshold so it might be totaly wasted and you'd have no idea. a new cat can burn raw fuel that your old one is letting blow by.