Welcome and dump the K&N I would also send off a oil analysis on your next oil change. You won't believe what they can tell you about your engine!! Do you know if it is a early or late 99? There were many changes made mid year. You probably only have the puny oil to air trans cooler, I would get gauges ASAP, although from the bed it looks like it was used to tow, so the PO may have added the cooler in the rad, or another OTA cooler. I would change all fluids and filters ASAP!! Just something I do with every vehicle I buy.
NCH