Maybe the wing and stab incidence is off? It's typical for these planes to have some type of coupling. It just depends on how it was built from Hanger 9. You can usually add mixing (a little up elevator with rudder) to fix that but not if it's really bad. Possible the engine thrust could affect it too.

Here's a test for proper engine thrust: Pull a vertical line 100 feet in front of you. Do it on a day with little to no wind. Make sure the cross wind is hitting the side of the plane if there is any. Watch the plane. If it pitches towards the wheels, it needs a little less down thrust. If it pitches towards the canopy, it needs less up thrust. You should be viewing the side of the plane as it's going vertical. You can do the same thing for left right-thrust but pull vertical at the end of the run way and view the top of the plane. Make sure the wind direction is following the runway (left or right). And of course make sure your rudder is centered and don't move it during the test.

Joe