Not likely at all. The MOI’s are almost identical. The STi is 12.9413 and the TS2 is 12.4697. The difference in those two numbers are statistically insignificant. Could not tell you why you are experiencing what you are experiencing without seeing you and possibly doing some in depth analysis of the clubs. The horizontal cg location variance in those clubs is insignificant as well. Offsets are almost the same as well. Even though they are “identical” builds, there could be some variance in the shafts, but even that would be a stretch. Just know that in my 43 years experience in designing, building, fitting and playing clubs of all types, sometimes why one club performs one way and another performs differently even though they are the same or very similar, can not be determined. I wish I could give you a definitive answer, but based on the designs and the information you provided, I can’t.