Check the vacuum line to the transmission modulator at the right rear of the intake manifold. On US versions this is a white , vinyl hose. They are prone to pop off when the black rubber connecting hose deteriorates,and the engine has a lean backfire. Also there is a rather large plugged port on the top at #2 cylinder intake riser that may have become dislodged , and yet another smaller one at # 5 (or 6)again at the riser. If the roughness is subtle in nature, the problem could be in the EGR vacuum plumbing. Try disconnection from the EGR whilst it's running and cover the hose w/ you're finger. The surge in the idle sounds like a large intake leak.