Sharad, I'm not sure I understand the situation, but IMHO;

Nearly any plane trimmed for level flight at a constant powersetting, let's say at half throttle, will begin to climb following an increase in power, as the trimmed condition attempts to maintain the trimmed lift condition, and hence, the airspeed at which it had neutral. It will also descend when power is reduced, for the same reason. One trim setting will not maintain neutral at all airspeeds. I generally trim for a 'cruise' power setting, ie. the one which I expect to have most of the flight, and hold forward or back stick as required when flying faster or slower during manuevers. Depending on the model I'm flying I may re-trim to neutral for landing approach speed, but usually not.

A need for changing thrust angle can be determined by establishing trimmed level at less than full throttle. If the aircraft pitches up when throttle is quickly raised to full, this can indicate a need to add some down thrust. Conversely, from the same trimmed condition, if quickly reducing the throttle to low causes the nose to pitch down suddenly then some up thrust may be needed. Using the same rapid increase or decrease of throttle, and noticing if the nose pulls left or right, can else help identify a need to adjust thrust angle left or right.

I'm not sure, but I believe that a wing or stabilizer incidence problem is indicated when the plane wants to pitch up or down (not necessarily climb or descend) with changes in airspeed. Perhaps someone more knowlegeable than I am can explain this.