I agree with steve and add that i have never heard of a solid EGR blanking plate increasing hesitation - onlly reducing it
As steve has said - if you clean out the the inlet manifold it may sort it, i recommend you fit a new air filter (if not done in the last 6months/6k) and reset the ECU (not the trip computer) for the ECU to "relearn"
Maximum torque is just below 2500rpm and there is often a "step" in the power delevery arond here, the egr can "soften" this power delivery by increasing turbo lag (as some energy that would utherwise go to the turbo is lost through the EGR
So the power delivery below 2500 is similar pre and post (solid EGR) blanking plate, but above 2500 the blanked motor pulls stronger as there is more boost available this may be more noticable in some gears than others ( so the extra power/ torque above 2500 is percieved as less under 2500)
look at the extreme step in the torque curve - with very little torque below 2k- then peak torque about 2.3-2.5k, and the remap increases the torque above 2k/2.5k - but not below 2k - the plate can have a similar (but a bit less extreeme) effect -
although the EGR has a specific operating range (ie- under 2k on some engines) it can affect the engine throughout the enire rev range, as the energy lost through the EGR opening is never fully recovered (as the engine revs through the power band- the turbo has to "catch up" with the engine)
Just to point out the standard boost control system(s) are still in place (actuator/ VNT etc) and it just boosts quicker (but not more peak boost) with the solid EGR blank - so its safe/ will not cause exesive stress on the engine
Let us know how you get on