I have started seeing speed this year. The trap that is sounds like you are in is a common one. We spend so much time talking about slowing down and learning proper technique, that we forget how to race fast.
When Alex Popov was winning everything (late 90s I believe) he was swimming very long slow strokes (about 0.6s per arm, Coach Shinji measured). Most of his competitors were racing at 0.4-0.5 seconds. When I started learning TI, I slowed down to 1.5seconds per arm to get it right. There is no way I will race fast at 1.5s.
So I started doing three things.
1. Build swims. As part of many warm ups, I do 50s where I start very slow and build my tempo as I swim. My goal is to finish as fast as possible with the same stroke count on both lengths.
2. Golf - swim a 50 and count strokes. Add them together. The next 50 must get a lower total either by going faster with the same count or the same speed with fewer strokes. (THis was always really hard for me for some reason.)
3. My most successful approach. Use the tempo trainer. Find the stroke rate that you are currently swimming with the least effort and good technique. Then increase tempo in very small amounts (0.02 at a time) each 25 while holding the same stroke count. See how far you can go. Then, when you get to your limit, stay at that tempo until it feels easier.
so for me, I usually start at 15 strokes (25y) at 1.1 and on most days I can descend to 0.75 without adding strokes. I have gotten as low as 0.6 once after swimming daily for a month. I also noticed that when I went back to 1.1, I went down to 14 strokes. So now I have to play golf to see if 14 strokes at 0.85 or so can get me faster than 15 at 0.75. It becomes a game to find your optimum. And its a fun game.
These sets will train you to hold your technique while increasing speed.