The Renault engine issue

I couldn't just understand when Briatore sort of complained that his team were left behind in the engine development during the 2008 season. The FIA has told you what not to change and it has also told you what you can change. You don't change things and you pay the price. He claims Renault took the rules 'as such' hinting at being too naive or some thing. I can't do anything but laugh at these stuff. Okay, granted you take the rules as such. Then why do you want to tune your engine now? Is tuning the engine gradually as the season progresses less naive and less 'aggressive interpretation of the rules' than throwing in a bunch of upgrades at one go in the winter?