Just like 05 said you can buy a gt bumper and do it or cut them out. I think it looks wayyy better with the bumper. If you don't want to buy a bumper or start cutting on yours, you can always run it under the bumper.
That template is in a PDF fille on this web site somewhere , Run a search that is how I found it , I made a copy of it then it was used to install my other brand pipes ,, worked perfect
Also... GT takeoff bumpers are fairly easy to be had. You can even once in a while find them in your FACTORY color and won't have to have it painted. I purchased my gT500 bumper on craigslist for $250, ready to bolt on. I would cut your factory one to begin with (free) and if you don't like it, then look for a gt, or other dual cutout bumper to please you. There are also rear valance's that you can purcahse that can hide the cutout and make it look more factory (I think cervinis sells one) that 3m's to the v6 bumper and gives you two molded holes.
What I did was cut my bumper first. I liked it, it looks fine, but the gt looks better in my opinion. I waited until I found a gt body kit on the web, and upgraded to the gt kit then. I found the front and rear bumper in my color for $225. It needed some work to the mounting bracket, but other then that I got a great deal.
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2006 V6 auto with the pony package
adding to it everyday
I had the guy at a performance shop install GT Duals on mine with silver ceramic headers and an x pipe last fall. also the sport tune. The GT exhaust were about 300 and he cut me a big deal on all the work.. I had flowmaster on it before that and the car was ok but that was before the upgrade. The shop guy cut the back bumper and it looks great. I upgraded the intake as well. I was not about to do it myself. I still have the flowmaster and another intake to get rid of somewhere that I dont need.
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GStang07
07 Gray Metallic stang v6 auto with dialbo sport tune, silver ceramic headers, gt duals, x-pipe. K & N cold air intake. future upgrade to wheels and better tires. It will always be a sleeper on the outside. Keeping the traditional look and am going for performance.