Are you talking about an actual PCM tuner like SCT, Edge or a $70 ebay chip?
Any decent brand tuner will run you $300 ish on up new and will see decent gains depending on your truck and setup, a $70 chip is a ripoff, just a .25 cent resistor chip in a pretty plastic box usually.
to see SCT Group Buy!
to see Edge Group Buy!
Message or call me direct at 614 620-5050 with any of your SCT or Edge Tuning needs!