I just installed 1-7/8 ARH headers to compliment my Maggie and they did just that. From what I understand you can still go pretty big beyond this and they will be just fine. Don't know the negatives on going with 2" except for the loss in boost, but that can be made up for with a pulley change. I was told to go 1-7/8 by a few different tuners/builders so that's what I did. Car is a MONSTER now. Very happy.
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Magnacharger TVS2300 / Roto-Fab CAI / ACT Twin-disc clutch + flywheel / Livernois Motorsports Duel Fuel Pump / Modified stock engine cover / ARH 1-7/8 Long Tube Headers + High Flow cats / Magnaflow 3" Cat-back / Eibach Springs / Pfadt Sway Bars / Stillen slotted/drilled rotors, hard lines and Hawk pads / Barton Short-Shifter / CBD Spoiler / GM Heritage Grill / Forgestar F14 20x11/20x9 Matte Black / Nitto NT05 Tires 565WHP/570TQ