For your coolant temp gauge, the kit would have come with an aftermarket sensor. you have two options:
1) mount the aftermarket sensor in the factory coolant temp senser location, this will result in a dead dash gauge
2) do this, and purchase an aftermarket adapter you can cut into your top coolant hose, to wire the factory sender up to, so the dash gauge works too
If the kit didn't come with an aftermarket sender, you may have to contact them to obtain a suitable styled sender, as you cannot use the factory sender and simply hook up the signal from that to the gauge. They work on different tollerences and you will get an inaccurate reading.
On a VR V6, the temp sender should be behind the alternator. It will be the smaller of the two senders back there. The large one will be for the ECU, the small one is a dedicated signal for the dash gauge. This is the one you want to replace.
Oil temp I would presume is best hooked into a T-Piece on your factory oil pressure switch, which is located down the bottom left of the motor, not far from the oil filter. I would assume you'll have to go and purchase an appropriate T-Piece to fit both the pressure switch thread, and the oil temp sensor thread
Hope this helps.
