Leave it stock!!! TLs arent made for racing! Jus playing.
If u must do something to it go with a K&N drop in and a decent exhaust system with high flow cats.
I keep my TL completely stock except for tints and rims. If i want to go crazy i just drive my accord.

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My first video of my car!!
1995 Accord lx Turbo (weekend warrior current money pit!)
2005 Acura TL WDP 6-speed Navi (traded)
2008 Acura TL WDP Type-S 6-speed (new baby!)