The level brackets for holy wrench bonuses are actually incorrect.
Ash says all it does is make the formula use 27% instead of 25%. So it'd be ((level/100)*27)+7. This works out to these boosts at these levels (bearing in mind I think there's a mid level prayer req on the quest, so the low levels with no boost don't matter)
01=0 02=0 03=0 04=0 05=0 06=0 07=0 08=0 09=0 10=0 11=0 12=0 13=0 14=0 15=1 16=0 17=0 18=0 19=1 20=0 21=0 22=0 23=1 24=0 25=0 26=1 27=1 28=0 29=0 30=1 31=1 32=0 33=0 34=1 35=1 36=0 37=0 38=1 39=1 40=0 41=1 42=1 43=1 44=0 45=1 46=1 47=1 48=0 49=1 50=1 51=1 52=1 53=1 54=1 55=1 56=1 57=1 58=1 59=1 60=1 61=1 62=1 63=2 64=1 65=1 66=1 67=2 68=1 69=1 70=1 71=2 72=1 73=1 74=1 75=2 76=1 77=1 78=2 79=2 80=1 81=1 82=2 83=2 84=1 85=1 86=2 87=2 88=1 89=2 90=2 91=2 92=1 93=2 94=2 95=2 96=1 97=2 98=2 99=2
I have personally tested this at level 88,89,92,93,96 and 97+
176.68.70.130 00:21, August 10, 2016 (UTC) Zer0
Holy Wrench Hidden Bonus[]
It's not speculation, it's testing.
I heard some talk about a hidden boost on the Holy Wrench that slows your prayer drain.
I then went and tested it for myself, by using a prayer with the wrench and seeing how long it takes for me to lose 1 prayer point.
Following that I did the same test without the wrench.
The ending results, there was a different rate in which I lost prayer points - with the Wrench, my prayer lasted a little longer.
How is that not firm evidence? You can try it yourself assuming you have Holy Wrench.