John Deere 111 carb adjustment...?

I blew the Briggs 11hp in my old JD111. So I swapped engines from an identical JD111. The replacement motor ran great before the swap, but after installing it in my good mower, and swapping the carbs since the old carb looked in better shape than the replacement motors' carb, it now runs absolutely lousy. I followed all the low idle adjustment directions and set all the adjusters and backed them out 1 1/4 turn, it fires and runs decently, but very high idle. Once giving it even a tiny amount of throttle it coughs and sputters like it's getting way too much fuel and then it starts to take off like it's going to tear itself to pieces, as if the governor is help open. I've gone back through and checked and rechecked all the linkages, settings, cable, etc. and just can't seem to find the problem. Does anyone out there have an idea about what to look for? Thanks.