Furnace short cycling

UPDATE, from factory this suburban SF25 had 3 ducts, 2x4" and 1x2". Way to go on factory build quality. I have the furnace fully installed and running the way it should. I installed 3x4" ducts that come out of kitchen cabinets with about 2 to 3 foot of ducting. Changed the limit switch to the sf25 model prior to a build date if 1992. They ran 175 degree and after 92 they are 160's. The build diagrams between those years look to be identical. They also didnt have the exhaust and intake ports properly fitted into the outside sleeves and hot air was pumping back into the air space around furnace. Cranked the heat to 90 degrees, opended the doors and ran furnace for 1hr straight. Temp at vents was 140 degrees compared to the 167 i was getting before. After 1hr running I can still hold my hand on any part if the furnace shell. No more limit switch cycle, temps are good. Housing is running alot cooler. Thx for the input. I'm calling this one fixed. May switch to a wall mount thermostat with less variance as I find the carrier V has too much temperature swing from what it's set too before furnace kicks back on.

Cheers.