2004 Echo rough idle

Hi,

My girlfriend have a 2004 Echo with a manual trans. It has a slight rough idle, sounds uneven and, how could I say, a bit helicopter-ish. The car has got 220 000km, plugs are new, rear o2 has been replaced recently because it had set off a DTC. I checked the fuel trims after a cold start, it idles good on startup, but as it warms up it starts to run rough. With the car warm on idle the LTFT are at 20%. They go down to about -2% when a give it 2000-3000rpm. Tried to check for vacuum leaks with brake clean around the intake and throttle body. The STFT did react negatively form 0% to about -6% when a sprayed around the throttle body. I replaced IAC and throttle body gasket to no avail. Now thinking to get the intake manifold gasket, I know I should have done it while I was already there but what da ya want…. Also, the car’s got a leaky exhaust manifold gasket (small) which I don’t really thinks affects anything. As of now, there’s no active DTCs. Car fuel system runs in closed loop and from what I can see with my scan tool, front and rear o2 sensor reading are normal. Front fluctuates between 0.1v and 0.9v and rear pretty much stays low around 0.1v when the car is idling.

Any other ideas I could have missed?

Thanks