yoteracin

I Read an issue on the forum aboout replacing the power transistor so I bought one but cant find where it goes on the vehical any ideas?

I am a first time pathy owner I love it, my problem is It starts fine cold idle 1300 to 1500 but when I step on gas or put in gear you have to feather the gas peddle to keep running any ideas on what the problem is? has new plugs, wires, coil air cleaner, fresh oil change, new fuel filter its like a flat spot in the carburator but this is enjected so i am confused can anyone help thanks