Does the cam have to be 100% stock or just have to have the same lift advertised duration lsa but can be ground with more aggressive profile ? compression generally gives 3-4% for every point of cr, with a bias to gains at lower end of cr like going 8.4 to 9.9 than 12.4 to 13.9 the hp gain % is slightly higher for the !st. Valve job and tuning is probably where it's at engine wise, anything you can do to lower friction, pumping loss, efficiency etc..
It's all the little things you can do to add up to improve e.t.s, probably more comes down to the rest of the car, drivetrain suspension etc.. since performance is somewhat fixed.