Right, mission 9 is a major pain in the ass. Marconi (your ally) is an idiot who will refuse to aim at anything properly and who will drive into bomb blasts and bullets. My advice is use the bombs smartly, be prepared to get behind (and in front) of Marconi and ram the difficult enemies off the road. Also, let him get as many of the tool kits as he needs otherwise he will not make it out of Detroit. And once you complete the mission, get at least three of the level 9 upgrades before taking him on in hard.
Oh, and some of the things I've achieved I'll have to achieve again because I achieved them before they became achievable. Bugger.