Can't say I have noticed any performance hit so far. No extra noise. I was expecting some extra noise from the compressor when it runs, but as I mentioned earlier it seems to be quieter than before actually, must be the new bracket. Otherwise no "new" noise reverberating in the cabin.
One thing I would recommend is slamming the doors pretty good after you are done installing both sliders and fuel tank. Mine made an annoying metal vibration noise right after the guys at T44 were finished, easily corrected by adding metal washers to a couple of bolts holding the fuel plate in place. The bolts, although fully tightened, still left enough play for the plate to slightly vibrate against the RH slider. The metal washers took care of that play, and the car as been a tomb since.
Fuel usage seems about the same as before. I have done the math, between the two rock sliders (about 200 lbs for both) and the fuel tank plate (about 60), plus the extra battery I put in yesterday in the engine compartment (40 lbs) I have added about 300 lbs of sprung weight with my mods. That's a lot, but not enough for this car to notice given the prodigious engine and wonderful brakes. If gas mileage has gone down a 1/2 mile per gallon, I'll live. My brakes may wear out faster now, but the car still stops on a dime like before. And I can feel I definitely lost a little pep from a standstill, but I didn't buy this car for 0-60 sprint times. For the amount of protection I gained, I am willing to put up with the drawbacks. It's my daily driver too, lots of miles. I've had her for just over 4 months and I have over 10K miles on her already.
