After a long time coming I finally did the Tundra 231MM upgrade after going through a few paris of rotors. it was a super easy Upgrade, I bled the brake fluid throughly and am pretty sure theres no air in the lines however the pedal travel seems pretty long and is not firm at all. Eventually I can get them to engage but not what I was expecting.

Ive read a few threads regarding this issue. So my course of action is this:

go to a dirt road and stop so that it engages ABS to purge the system of air and then re-blear.

the truck was a 2WD SR5 with 15" steel rims, I've read that my caliper cylinder bore is actually smaller than the other models from that year 43 vs 45.5mm so would a fix be replace the master cylinder with the other 4Runner MC to a tundra mc? to be able push more fluid?

I just did this upgrade too. My pedal feels fine to me though. Sometimes it will help if you bleed all four corners, starting with the back right, then back left, then front right, then front left. After bleeding mine and bedding thing brakes properly the pedal felt good to me.

If you don't have a brake bleeder get a buddy or family member to help.

95% of the time poor pedal performance is due to air in the line. I would do all 4's like stated. Make sure someone is pushing down on the brake before you crack open the bleeder, this helps it push the air out. Good luck.

What they said, then check the adjustment of the rear shoes.

We had to bleed twice even tho the first time we pretty much flushed the entire system.

I bled the system throughly (old stuff was really, really old.) and am pretty sure that its airtight. However I did find some info over on Yotatech which helped.

basically go onto you street drive a little then stop, turn off the engine and pump the pedal 25 times. Start the truck back up and drive some more, then repeat 3-4x.

another possible solution would be to go to a dirt road and hard stop to engage the ABS and that would supposedly flush out the air then do a re-blear.

I did the first one the day after the swap and it brought the brakes back to what they felt like before but with the extra grippy tundra gear. So, I'm pleased. I might try the ABS possibility as well and then do a re-blead.

i did the upgrade a few weeks ago.. Speed bleeders is the way to go.. 15 bucks for a pair.. Just the time alone and being able to bleed them myself was worth it..

I also tapped the calipers with a mallet to get just in case there were air bubbles trapped.

It should not feel mushy at all.. infact mines felt firmer.

yup, SPEEDBLEEDERS. makes the process so simple and quick and easy, actually a pleasant experience.
Speed Bleeder Bleeding Brakes Bleeding Motorcycle Brakes Automotive Bleeder Screw Brake Bleeder

my bleed didn't work properly until I did the rears with the key in the on position, engine not running. Something about a pump needing to be powered up. After that the brakes felt great. Before this I tried bleeding twice and while it seemed to go fine I had the same mushy pedal thing you have.
make sure your parking brake is disengaged.

Engaging ABS on dirt roads worked good for me. Glad you figured it out.