What cam should I get?

My spark plugs have never been cleaner since I install a MSD 7al box and a MSD 8251 coil. They are so clean theres nothing to sand or clean after 6000 miles on them. They do wear out faster, cause I install them at .040 gap and after 6000 miles the gaps were almost .050 so I got new plugs. My gas milage does stink however.