I put mine in the cab, under the dash. It is much easier to run the wires with it under the dash. If it is under the hood you will have to get that big plug through the firewall to plug into the gauge. My ISSPro EGT has 2 x T5 bulbs, so if you are getting the bulb covers, make sure you get 4, one on each bulb doesn't seem to change the color enough and the gauge still appears white. 2 covers on the big bulb in the boost gauge did the trick, I need 2 more little ones for the EGT gauge, I'm still waiting for them to arrive.