in WOT mode the pcm ignores the O2's and feeds based on progammed fuel maps.
a cheap 65 dollar tune is to add fuel pressure on return cars(87-97) 98's use hybrid setup.
it does the same as a tuner to some extent. it will improve power from an A/F ratio stand point.
the mods i listed are cheap and efffective. they are the first i did on my 96. makes it feels like it had some power. my guesstimate at the time was 245 flywheel hp vs. 215 stock.
165 for cheap "X", 65 for regfualtor, and 200 for gears plus installation. now is a time to learn to do your own stuff BTW.