I know I can use head pipes on my '98 FLHT from years up to '08, but cannot use '09 & up.

Can anyone explain to me EXACTLY what the difference is as to why they will not work?

Thanks.

 

They run under the bike and that is where it looks like an "x", the collector may we call it??? That would lead me to believe there is nothing but a bracket mount missing on your frame and the bracket being way, way off on the pipes. I would guess the pipes would line up to the heads. I have not read that twinkies have a different mounting pattern since 2009. Look at it this way, you own a 1998 so you're not entirely comfortable with the phrase ' it don't fit'. We all get you.
If you're getting free take-offs then grab 'em and see what needs to be done.
Good luck