Don't feel too bad as this is common. A steel bolt in aluminum with a little corrosion and this is the result. DO NOT REASSEMBLE WITHOUT FIXING!!! You will never get the engine to run smoothly as you will have a major vacuum leak. There are two avenues left to you. Don't try to muscle the bolt out with a stud remover or vise grips, you will just keep breaking off what's left. Either weld a nut onto what is left (if there is enough left) or drill it out. If you weld a nut on before trying to loosen it use a torch and heat it up as much as you can. If drilling it is critical to stay centered and straight. Start with a small drill and work up. If you totaly screw it up oversize it, thread some aluminum, screw it in and with the air intake plenum in place mark and redrill and tap a hole. If you manage to drill the bolt out but mess up the threads use a thread insert to fix it up but only if it is centered and straight. This is really a job for a machinist so be careful and go slowly. When reassembling use Never-Seize so this won't happen again. David Teitelbaum vin 10757