Trying to replace plugs/wires on a 2001 Grand Prix, but the old wires are totally stuck on the plugs, like they're welded on. To complicate things, the boots are inside these metal heat shield things that GM uses (my other car has the same thing), so I can't put a vice grip on the boot without crushing the shield, which no doubt is a highly expensive dealer only item (it's just a metal tube the boots fits into). Car has about 90K miles, I'm pretty sure the plugs/wires are original. Is there any trick to blasting the wires free?