First, my HKS exhaust is becoming discolored in some places, anybody got any ideas on how to fix that? I tried Never Dull and it didn't work

Second, I want to run Crower Stage 2 cams, do I need a standalone, or are they safe to run with a piggyback, just tuning the AFR?

 

hmmm... never dull would be a good choice-
was the exhaust cold when you tried to clean it?

 

Well even though this is the wrong forum to ask about performance mods. The crower cams have been proven to not provide any gains. Automotive speed the vendor who hosted the original group buy refunded everyones money. Try contacting hytec they supposedly have some cams that make decent gains.