What are some important things to tune up on my 99gt

What are some things I can do to tune up my 2.5 got besides oil change, wires, and air filter It has 85,000 miles on it

Change out the coolant to stop corrosion, good for head gaskets. Change out the brake fluid to get rid of intruding moisture. If it is ABS, I'd get a shop to do that. Fuel filter. Change out trans and diff fluids. I expect you meant plugs along with those wires. If you aren't experiencing any specific age related suspension sounds or problems, then there is nothing to do there. Paint and interior plastic care. Check everything for dead light bulbs. I'm sure there are lots of other things. Are you just trying to care for the car or are you experiencing some symptom?

I was just wondering if there were any sensors or anything like that that should be addressed. I just did a full custom color paint job on the car and now I’m trying to just get everything else taken care of. I don’t have any major issues with it. I’ve been putting in a lot of work on the car. I’m redoing all the suspension and brakes.

I'd replace all of the vacuum and rubber lines that you can find, even with low miles, the car is old and rubber gets brittle. Just but 6ft + of a couple different sizes and just replace everything you can see. Also, I'd replace the fuel filter and the fuel strainer, the strainer is in the tank but the access panel makes it easy to get to. Other then what Chaz said, I'd just clean and degrease everything and clean the throttle body and MAF sensor.

I would check over the CV boots and steering/ tie rod bellows as if they are original, they are likely cracked or splitting due to age.