93 lexus GS300 - how do i change the spark plugs

It's not the trac control, it's the throttle body.

You need to get access to the two middle plugs by either taking the throttle body off or unscrewing the screws that make it come apart into two sections. Be careful, there are some very long screws that hold it together and it slides off those screws. There's a lot that you'll have to undo, if I remember, there are some hoses attached to the bottom of the throttle body which have to be detached before you can slide it off. Basically it's a pain in the ass but it's doable. I found some GS300 service manual pages on one of the sites which show how it comes apart, but I didn't really use them. It's been a few years since I did that.