I understand this frustation too. I have a terrible time not racing the way that I use to with a few nods towards TI.
I swam in high school and have only been swimming TI since late November 08. My normal practice is usually very slow and attempting to swim with TI perfection. Because I was not following the drills to increase speed, when I raced I would fall back my high school style stroke (slightly improved).
To correct this, I have been trying to follow the advice in the Total Immersion and Extraordinary Swimming books on timing and swim golf, so I have two different "race" strokes.
In my old stroke, I burn all my energy and when I am done, I want to throw up from the energy spent.
In my new stroke is hard for me to maintain, because my core only moves so fast, and I have more energy available. So even though I am moving as fast as my body currently allows from side-to-side, I always feel like I am holding back. If I "stop holding back" my stroke collapses back into egg beating. This is not to say that I am not extremely tired when I race this way, but I do not burn through all the glucose in my body when I do it.
Luckily, my new stroke is a fast. It times at 1:10 on the 100y short coarse and my old stroke was best timed around 1:15y short coarse. My goal is to break one minute in free and butterfly on short course be year's end.