I just started my second playthrough of ME3 with a second ME2 imported character, and on Mars, I still didn't pass the rep check for The Illusive Man. My Paragon bar was basically full in ME2 (I passed the Morinth check). I started with total rep slightly below the first tick, which I assume is what's required to pass that rep check, and quickly surpassed it during my first visit to the Citadel. My question is how can I make up the difference before speaking with The Illusive Man, or is it even possible in my case? Is it only possible with an imported ME3 save?
Its possible to do it with an imported ME2 save, I just did it recently on a new playthrough. I didn't check to see what my rep was at the time, but all I know is I was able to choose the paragon option.
Also, you may want to consider going back to redo this choice if you can:
In order to persuade the illusive man at the end of the game you'll need to have passed every paragon/renegade check in the game with him, this one also counts.