Douse those suckers in some Liquid Wrench/PB Blaster/etc. and let them sit for a bit. That may help loosen them up. I sprayed mine down the night prior and then a lil more just before doing my headers. All came out with no issues.
Sent from the Death Star.
2012 Kona Blue 3.7L V6:
Borla LT headers, O/R h-pipe, Borla S-types, 3.73 gears,
Steeda adjustable UCA w/ mount, BMR LCAs, Airaid CAI,
LCA Relocation brackets, AE driveshaft, GT 80mm TB,
Black 18x9/10 2010 GT500 Wheels w/ Nitto NT555s,
Eibach Sportline Springs/shocks & Koni STR.T Struts