Xtreme2damax do you have the same problem with the hall of resident evil remake?
this was my problem, i had fullspeed with rebirth but in some areas like the hall the framerate drop to 17. i disabled idle skiping and now i have a solid framerate of 25 fps (PAL) maybe you should try disabling idle skiping
Idle skipping is disabled and this is a widespread problem for everyone with Twilight Princess, even those with the most beastliest and powerful machines. I don't get slowdowns in Resident Evil Remake with Copy EFB to Texture enabled, but I do get those slowdowns with Copy EFB to Ram enabled in Resident Evil Remake.
I can confirm this bug as well, works fine outside of hyrule (dungeons and such), slowdowns in map itself.
So many people reporting this, yet no one is stepping up to perform the tests skid requested so this issue could be fixed.
Looks like the developers may be left doing all the work debugging and testing this issue, but that could take a while. It would hopefully be sooner instead of later if a member ran the profiler tests that skid requested and posted the results.
I'd do it if I knew what the profiler is?
Vtune seems to be the best choice, so far all the freebie profilers are inadequate to perform the tests skid requested. I tried using the free trial of Intels Vtune profiler but I think the trial is only limited to a few seconds of profiling and I can't seem to change it anywhere.
Well, I don't think someone would buy that software (look at the price)
Anyway, I've downloaded it, and it's working (you can configure the time u want Vtune to analyze) but it'll take some time to get after the twilight, I don't have the NTSC version, and when i try to finish it Dolphin shows a "Dolphin has terminated..." and I forgot to save the game.
I'll do my best to do fast

You are using the free trial correct?
Can you tell me how to change the time?
Yes ^^ the 30 day trial.
When you start Vtune, click on File -> New Project.
-Select the Sampling Wizard -> Click on OK (or double click on Sampling Wizard)
-Check the Windows*/Windows* CE/Linux* profiling
-In Application to Launch set the Dolphin.exe dir
-click on Next, Next and uncheck "After a duration of "20" second(s).
Then Terminate =)