Tractor is a 1949 front mount. A brief history is that this was a great running tractor before I changed a leaking exhaust manifold around number 4. Since then I have had loss of power and could not do anything without getting a black soot all over my plugs. It is so bad you can see it coming out of the exhaust connection. Tried to no avail to adjust the carburetor. Memebers here thought maybe it was damaged by not laying it upright during the manifold change. Had the carb rebuilt by Royce with identical results. I can get 400-500 rpm at low idle and 2200 at high. Followed Dell?s carb adjustment instructions. I have spent hours in the field moving the needles 1/16 at a time and I can get marginal improvement by enriching idle screw which is not helping my sooting issue. Tractor starts and runs great with no load. Any load and it has trouble, even reverse taxes it. It has also developed a knocking sound which seems more centralized on the carb side and closer to the oil pan although the oil pressure remains the same. Removed belt to eliminate water pump and it had no effect. Pump is ok. Tried a different distributor on the tractor trying to eliminate an electrical issue. The plugs are gapped correctly, the spark is strong, wires are on right. All new parts in distributor, points gapped at .015. Followed Bruce?s diagnostic procedure with the test light and it all checks out. Points open and close properly, used a jig to set static timing. If it?s not a carb or electrical issue where would you suggest I go next? Or am I missing something in the carb or distributor? All thoughts encouraged!