As far as organizing them, I'd say to categorize similar to this:
.Exhaust Manufacturer-Brocks
. Exhaust Model-Alienhead
. Slip-on
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
. Full Exhaust 4-2-1
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
. Exhaust Model-Street Meg
. Slip-on
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
. Full Exhaust 4-2-1
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
.Exhaust Manufacturer-Tsukigi
. Exhaust Model-Cannon
. Slip-on
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
. Full Exhaust 4-2-1
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
.Exhaust Manufacturer-Ti Force
. Exhaust Model-Sumo (?)
. Slip-on
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
. Full Exhaust 4-2-1
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
. Full Exhaust 4-2-1-2
. Stock Filter
. Aftermarket Filters
. K&N-Street
. K&N-Race
. BMC-Street
. BMC-Race
. PiperCross
You could make separate pages for each exhaust manufacturer to keep the page length down, Then make the "Filter" the active link. Don't forget the TRE option
I know there are many more variables, such as 87 octane, MR9, nitrous, etc... This is just a base setup. In that case, Id probably just make it a sub category at the bottom of that specific manufacturer. Also for things like added timing and fuel tunes or the race tunes, you could make the individual "Filter" links go to a page with all options for that particular combination; nitrous, 87 oct, MR9, etc... Same could be done at the diverging point of Stock Vs Aftermarket filter. The main page could be structured
.Exhaust Manufacturer-Brocks
. Exhaust Model-Alienhead
. Slip-on
. Stock Filter
. Aftermarket Filters
. Full Exhaust 4-2-1
. Stock Filter
. Aftermarket Filters
Once they choose base filter tyope the entire list of associated tunes displayed.
A billion ways to do it. Just pic one and run with it. People should be appreciative that you're hosting them, however they are organized.