99 cars call for a different type of fluid as the pump/PS changed from 98. AT205 works great for leaky racks. BTDT. Over time the PS reservoir will 'weep'. You'll think you have a leak. And you do, sort of.

I use Valvoline Max-life synthetic ATC (red). Also use it in the auto-trans.

Search is your friend here. Lots of posts re: P0455 including several of my own.

Smoke is also your friend....