Electrical Issues

Recently purchased a 1kz Super Custom Hiace, unsure of year. Most electrics work and the car runs well, it also appears to have a brand new alternator. However when the engine is revved up all dash lights come on and other electronics work sporadically, any ideas on what the issue might be before I dig any deeper?

When that happened to mine the cause was the alternator although that had just been replaced. The auto electrician found that one of the brushes wasn't seating correctly.