I run my plugs at around .030 on my Paxton, which makes about 16 psi. I also run plugs that are probably 2 steps colder than stock and use cut back straps to expose the spark better. I believe they are Autolite AR3933's. Never had a problem with them. I only change them out every year or two just because I believe it's good maintenance. Never had a spark/ignition related problem with them.
You could also be having some belt slip issues. That will also result in a "wavy" dyno graph. Try to log the boost next time and see if it's wavering up and down at the higher rpms.