I've tried 26" tall ET Streets and lost mph with them every single time. My 60' times were just as good with the F1's (Low 1.8's). I then did a dyno comparison between F1's and 26" tall ET Streets. The results I got back in March of '03 were:

F1's: 447.2 RWHP, 576.5 RWTQ

ET Streets (26" X 11.5): 429.5 RWHP, 544.2 RWTQ

I switched to Hoosier Quick Time Pro's and the mph went right back where it should be, and the 60' times dropped into the 1.7's first time out.