Hey guys. So my little 1952 8n (side mount distributor) is causing me some stress. It cranks, and runs great in the shop but cuts up something terrible when I take it for a spin and open up the throttle to 1/3 to wide open position. it almost sounds like its miss firing. This is a long story but here goes. It is not a fuel problem. The fuel is flowing fine to the carb. It is not the carb. the tractor acts the same way with 3 different carbs that I tried. I went thru the electrical. New points ,condenser, cap, rotor and 437 autolite plugs. I ohmed the coil and got good reading. I checked spark on all four cylinders with a spark checker and got a good healthy blue spark on all four. I straight wired the ignition switch to check for bad switch. No change. I bypassed the terminal block where ignition hooks up to check for bad terminal block. No change. The points are set at 16 to 18 thousenths as I learned a few years back that the tractor will not run on the factory call out of 25 thousenths. Now a good friend has suggested that I pull the intake/exhaust manifold, that it make possibly have a clog in the intake part of the manifold. He said he had seen that several years ago on a farmall cub. Oh yes just one more thing. I can take the high speed adjust nozzle completely out of the carb and the tractor runs perfect. Remember I said I had tried 3 different carbs and they all act the same way. Pulling the manifold will be my next move I guess unless someone offers something else to look for. Thanks in advance for any help or advice! PS I cant see any sign of a cracked manifold or an exhaust leak.