My car is a 1.9CDTI [150]

I have recently had new timing belt, clutch & flywheel on it.
The problem is an intermittent lack of power in 1st and 2nd gear and it sometimes pulls back when accelerating. The EGR valve is unplugged and blanked off so shouldn't be a factor here. I cleaned the boost sensor at the weekend but that didn't solve the issue and I replaced the fuel filter before christmas.

Has anyone got a pic of where the swirl flap thing is located as I can't seem to find it. Could this be the 3rd injector plug?

Thanks in advance