I purchased a aftermarket oil pressure gauge of eBay . my 05 xl 2.3 doesn't have a stock oil pressure gauge . what kid of adapter do I need to purchase ? And where do I connect the the sensor to on the engine?

Your 05 should be a 2.5, at the rear of the engine on the side toward the driver down under the intake you should find the sensor for the idiot light, take it out and get a T fitting and screw it in, screw the idiot light in one end and the pressure gauge in the other end, you have to keep the idiot light or the computer will sence no oil pressure and shut the engine down.

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Apologies, I forgot the laters had a 2.3 double over head cam, but anyway you get the idea.