RTA      IGT
UltimaOmega07:  1:06:43 - 01:54
KyleDoesIt:     1:06:43 - 02:11
Difference:     0:00:00 - 00:17

First:
Omega:  08:51 real time passed between these two sections, and 04:10 in-game time passed.
        250 total IGT minutes, 531 real seconds
        521/250 = 2.124 (Average FPS of ~124)

Kyle:   08:43 real time passed between these two sections, and 04:11 in-game time passed.
        251 total IGT minutes, 523 real seconds
        523/251 = 2.084 (Average FPS of ~80)

It seems the time never advanced nor declined for either of us with a taxi warp, and there were many warps in this section.

UltimaOmega07:  1:15:34 - 06:04
KyleDoesIt:     1:15:26 - 06:22
Difference:     0:00:08 - 00:18

Second:
Omega:  03:54 real time passed between these two sections, and 01:52 in-game time passed.
        112 total IGT minutes, 234 real seconds
        234/112 = 2.089 (Average FPS of ~90)

Kyle:   04:08 real time passed between these two sections, and 02:28 in-game time passed.
        148 total IGT minutes, 248 real seconds
        248/148 = 1.675 (Average FPS of ?)

Doesn't appear to have happened to Omega, but seems to have happened to me once, maybe twice.

UltimaOmega07:  1:19:28 - 07:56
KyleDoesIt:     1:19:34 - 18:50 (08:50 without the +10 hours from death warping)
Difference:     0:00:06 - 00:54

Third:
Omega:  02:04 real time passed between these two sections, and 00:59 in-game time passed.
        59 total IGT minutes, 124 real seconds
        124/59 = 2.101 (Average FPS of ~100)

Kyle:   02:04 real time passed between these two sections, and 01:21 in-game time passed.
        81 total IGT minutes, 124 real seconds
        124/81 = 1.531 (Average FPS of ?)

Doesn't appear to have happened to Omega, but seems to have happened to me once.

UltimaOmega07:  1:21:32 - 08:55
KyleDoesIt:     1:21:38 - 20:11 (10:11 without the +10 hours from death warping)
Difference:     0:00:06 - 01:16

Fourth:
Omega:  02:25 real time passed between these two sections, and 01:05 in-game time passed.
        65 total IGT minutes, 145 real seconds
        145/65 = 2.230 (Average FPS of 200+????)

Kyle:   02:15 real time passed between these two sections, and 01:04 in-game time passed.
        64 total IGT minutes, 135 real seconds
        135/64 = 2.109 (Average FPS of ~110)

No taxi warps in this section for me. Two for Omega.
Additional info for a section within this section:
RTA: 1:22:30, IGT: 09:23
RTA: 1:23:57, IGT: 20:00 (10:00 without the death warp)
RTA: 0:01:27, IGT: 00:37 (Average FPS: Insanely high, like ~250, but that's obviously not what his average was)
Conclusion: He clearly went BACK in time with the second taxi warp.

UltimaOmega07:  1:23:57 - 20:00
KyleDoesIt:     1:23:53 - 21:15
Difference:     0:00:04 - 01:15