Got to the auto parts store and buy some gasket material that looks about the same and says it is good for manifold gaskets. Carefully cut a new one and install it. Do not overtighten the bolts, this will distort the flange. Check it with a straight edge and make sure it is ok.
Most peds will run without an air cleaner but some rely on the restriction of the air cleaner to enrich the mixture. Your best bet is to run the configuration that worked before the problem.