I recently purchased an '87 4000cs 1.8l and have done the following mods: Drilled airbox, K&N filter, Bosal free-flow exhaust, and a fuel enrichment module. I've been told the timing should be advanced at this point. 6 degrees BTC is the original spec. How far should I go? I've heard 12 degrees BTC.... Is it worth adding a cam without doing a head/valve job? Thanks in advance, Briand