do you have a picture of your pod installation yet? a common problem with fairings on aircraft directly in front of the tail is tail blanking.
how flat is your windscreen? if its not streamlined perhaps it is aerodynamically blanking out the tail, leaving only turbulent flow for the tail to fly through. i'd be careful if the pitch tendency is down, as that is a sure sign of tail blanking. this is why lots of light twins with a short fuselage have a high T-tail, to get the tail in clean air when at a high angle of attack. something is fishy. must be totally unnerving as the addition of power increases the pitch over...