I think you are in for a disappointment, if this is a simple device that hooks to the MAF sensor. Maf has adequately broad parameters and any device added will probably only risk your warranty without measurable gain. My opinion is from general knowledge and not experience with any specific device.
If you would like to affect performance you might consider an Excalibrator device with some professional advice on the programming.
What is this device you are considering?
Maybe you can benefit from the experience of someone on this forum before you decide. | 
