Hi Richie T, welcome to FTE!

To be completely honest, I would not have a lot of confidence that your spark plugs are installed properly. Using the right type of plug for your type of motor is vital. Gapping and torquing the plugs to proper specs is just as important. Maybe your mechanic was in a hurry or something, I don't know, but breaking a plug makes me wonder about the whole installation process.

The right spark plug wires, properly installed, are also very important. And a new air filter should be part of any tuneup.

You also might want to think about dumping a bottle of fuel injection cleaner (Chevron Techron gets good reviews around here) into your gas tank.

If it were my truck, that's how I would appropach the problem at first.

P.S. Do you still have a lousy idle?