Thought I'd post a couple pics of the starting point for my take on the new plenum. My effort is directed at improving the flow & distribution. I found this neat adapter for the T25 on Ebay for about $25. It uses a 2" charge pipe rather than the 1 3/4" in the kit. The 2" aluminum elbow has a larger radius as well. I'll connect these with a silicone coupler and sweep it back to a side entry on the plenum.
It would not be strictly a HP gain from better flow. A turbo works against itself if either the intake or exhaust side have restrictions. It appears that the intake side has a couple places that could be optimized. The outlet from the compressor wheel is 1.75" which gives a total cross section of 2.42 sq in. this gets impaired by each turn, the length of the charge tube, and the reduced inlet opening to the plenum. The 2" pipe has a cross section of 3.14 sq in, which is over 20% larger, will be shorter and have less turns. This should be; less heat, faster spool, less parasitic drag on the turbine and compressor. How much & at what rpm it makes a difference, we'll have to see. I also believe that the more you push the turbo the more critical flow becomes ( which is why porting gives bigger results on forced induction than on NA motors ! ).
I am part of the solution, I have been working on upgrading my bike for years. Which is why I came back to the forum, to reread posts looking to solve some issues...lots of good people on here with valuable solutions....when others are stirring crap...
anyway - my point was I thought you were referencing that the trask turbo that is part of his kit was a garrett gt 25xx turbo, which obviously it is not it is the journaled 1241 that is in the kit.
you see I thought you might use 25xx data when trying to solve the plenum problems and looking at what the turbo would flow under the curve... didnt want you to have more issues then are already present.
Here take a look at these 2 turbos and tell us which you have...
As you can see they are completely different. The bottom picture is my actual turbo GT25 the same as Rods.
Where are you coming up with that we have a 1241 ?
The 1241 is only good for up to 130 horsepower.