You mention that it used to happen before "until it got warm", and now it does it all the time until you're in higher boost? (boost is giving you more air to burn the fuel?)
Have you looked at your coolant temp sensor? (2-prong sensor on the water pipe)
What type of injectors do you have? Have they ever been changed? That leads me to the next part - "This car has mods to support ~430 RWHP" = jack shit. Please fill out your profile. =-D (It will help us narrow things down alot faster.)