I'm pretty sure most people like myself would trade you a stock already painted alpine white front bumper plus cash for yours. So you wouldn't be losing anything but rather gaining $500 or so and then you could reflect that in the price. Same goes for the exhaust.
I'm not sure why you would have to explain to a potential buyer why you have a stock bumper or exhaust. It's stock and wouldn't look out of place. As a buyer I'd be more worried about a modified car as opposed to a stock car.
Car for sale http://www.e90post.com/forums/showthread.php?t=881526
JB4 G5 - Forge FMIC - VRSF V2 DP - Magnaflow 15529 Catback Exhaust - BMS Clutch Stop - BMS DCI - CDV Delete - Dinan Stage 3 Suspension - 19x8.5/10 Forgestar F14 Gloss Gunmetal - Michelin PSS - M-Sport Front & Rear - M3 Side Skirts - OEM M3 Decklid Spoiler - BMW Performance Grilles - ZHP Shift Knob - M-Sport Steering Wheel - M-Sport Door Sills