I have the filter on my 98 LS and it works great. I have no problems and the gains are unknown if any.
I just cleaned it for the first time 3 weeks ago before i left for lex fest. It looked clean but did have a good amount of dirt trapped in it.
Get the K&N filter cleaning kit and spray just enough and then spin it in the air to remove excess before allowing to drip for a few hours before installing it again. It is ready to go being profiled when you buy it new.