if you can get a 'hotter' (overlap) cam go for it. The engine will idle more rough (depending on how 'hot' the cam is), but high-end perf will increase a fair bit.
Even if you advanced the cam, you won't get a whole lot of overlap. Turbo cars don't need overlap because they have high density air charges unlike the n/as. Overlaps allows the engine to 'scanvenge' for more air, through the exhaust valve and/or the secondary intake.
Your idle gets rough because some of the air/fuel mixture will escape through the exhaust valve during idle. low-end will also decrease.