Header extensions / torque tubes?

I don’t think with your weight of car that 3.5 collectors are doing you any good. Years ago I swapped to 3.5 collectors from 3 inch collectors and saw nothing. This on a 13 to 1 422 inch W5 motor that ran well into the 9’s at the same weight as yours. Surprised me a bit.
I am a believer that “ Torque Tubes” or header extensions, whatever you call them can be beneficial.
That is why I basically always race with very low restriction mufflers on my cars, currently Kooks, previously dynomax bullets, which can serve a similar purpose based on length used.
If you run open headers at the track, I would experiment with one or both of the above.
I have found these to be ultra trick…. They come in 3.5 too

3” Round Muffler 10” Long Body. Polished Stainless Steel. | Kooks Headers & Exhaust

FWIW.. I also leave at 2k off the foot and vert hits at 4900-5000, shift couple hundred rpm higher than you( I think..lol)
I never look at the tach when I shift, always by feel, that way I can be more consistent run to run, car tells me when to shift it