Can anyone tell me where the fuel filter is for a 1999 LHS? How do you change it? Thanks!!
Also I bought gas from a station and it started running rough in a few days. This only happens to the LHS. I put gas in my old 1992 F-150 from the same station just a half hour earlier and it has no problems. Is this just a LHS thing? It just seams it is more sensitive to gas that has a small amount of contamination.
Thanks again for any help here.

I do know that you have to put 89 octane in those and sometimes they will have a slight knock due to the gas. And with the fuel filter, it is in the gas tank I am pretty sure that in the trunk under the fabric there is a plate that can be removed to get at it, so you don't have to take out the whole tank.

Thanks so much for the info. I'll check this out. As soon as I find out, I will post an answer here so anyone else will know also.

Okay, this is what I found out. First, you cannot get to the filter from under the rear seat. It is best to get a shop manual, or Haynes Manual, or get a pro to do this job because you will have to remove the tank to get to it all. Really sucks!!!! Fortunantly after some more investigation I found that I had a bad sprark plug. Replaced it and it runs great!! The plugs were not that old, but I guese something happened when I installed them or it was a bad one off the line. Not sure. Just glad I got it running right again.
Thanks for answers.