di-electric grease that's cleare like silicon but wondered if it were to hinder the conectivity or possibly cause a short of some sort if there were too much of it in a connector. If it doesn't travel between the grease but the connection stays the same I would consider putting it on all connections even if they're brand new. esp the PTU, CAS, and injector connectors.
"Be kind, for everyone you meet is fighting a harder battle" ~ Plato