Would it be a good idea for me to turn my boost down to 12-12.5 PSI insted of 13.5 just in case I am really wrong about my specs? I use the highway alot and often reach max. boost, but never have any smoke except at cold starts on cool days.

I hope to have my car last me a good 5-6 years (Until I can buy an E270 CDI or E320 CDI in the USA) without having to dump a huge amount of cash into it.