lock up question

i have a 87 gn with stock 200r and it had a 3000 or 3500 not sure which one, and it was a non lock up. i did not know that about the car. it was in there when i bought it. it started a bad whining sound so i pulled the converter and got a new PTC 2900 lock up. and i love it no more sounds and works great. but it seems like after the trans warms up the lock up solenoid sticks i guess??? it kinda makes a lunging feeling when looked up. and sometimes doesnt like to unlock. then other times under really slow acceleration it shifts fast and likes right in at as even as low as 35mph. PTC told me when i bought the converter its a good idea to put a switch in the wires to keep it unlocked around town or racing. is that what i need to do or should i replace the solenoid or both? thanks everyone!