put on a smaller prop before you do anything else -a 22.8-
If it then runs correctly -or much better -you likely have the combo mismatched .
On the pattern planes -exactly the same issue existed.
the info on pipe tuning was from racing guys and TOTALLY incorrect for our uses.
I flew piped pattern planes also -in70's -80's etc.
peaky setups unless running at full tilt .
lots of power tho -
the DA50 will turn a 23x8 very nicely on matched pipe setups -- seen it .