Look, there are so many factors involved here that it can't be explained with 1 thing.
Of all those factors the highest one which would account for this matter, in my opinion, is the problems encontered in the pilot himself, not the plane. This is about 90% of how it is when "FM" or "Plane Data vs AH combat results" issues are brought up. A film, if you had one, would be a big help in clarifying this.
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This assumption justfies itself all the more since I have reason to believe you have no idea on the speed performance comparison between the Ta152H-1 and the Tempest MkV.
In Aces High, the Tempest MkV does about 388mph at sea level with war emergency power engaged. On the other hand, the Ta152H-1 does only 363mph with MW50 engaged at sea level. Yes, it is roughly a 20mph difference, but the Tempest is 20mph faster. The Tempest MkV is faster than the Ta152H-1 in practically all altitudes under 17k, except for the small margin between 9k and 13k. It is only over 17~18k the Ta152H-1 is faster than the Tempest. If you want to dispute this fact, you'd have to be a lot more specific than saying 'my 5 books say so', since I doubt anyone else has ever seen data claiming Ta152H-1 is faster than the Tempest at low altitudes.
And also bear in mind this is the Ta152H-1 we are talking about, not the Ta152C which was even faster than the H model and much more fit for use in conventional altitudes between 10k and 20k. It is more than likely the Ta152C your '5 books' are referring to if they indeed do claim the Ta152 is faster than the Tempest in altitudes between sea level and 20k.
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Now, in my opinion, this is what happened.
Analysis based on the event you have described shows that the Tempy driver was probably better than you. Either that, or just pure chance he lured you to an altitude where it was optimum for him, and disadvantageous for you. Despite you had altitude(=speed) advantage, the prolonged dive and chase effectively neutered the differences in E state. As you two both reached sea level the Tempest actually gained higher E state.
The moment you broke off, the Tempy driver, who probably was carefully watching your move probably did this: he more than likely also pulled off from extension and began to climb in a E-wise immelmann in to you. Since the Tempest is both faster and climbs WAY better than the Ta152H-1 at sea level(better, as in at least 1000 feet per minute) it is not surprising he would catch up with you.
I'd bet my last dollar that 1) you had wrong data, 2) you made a move you shouldn't have done, and 3) now blame the data for the mistakes you've done.
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If there is any explanation better than this, or a film that could prove me wrong, or have specific data on the speed performance of the Ta and the Tempy, please state it.