PM me with your email adress and I'll send you my personal an excell file I made to match your motor to a compressor map. You use the engine displacement, volumetric efficiency and desired boost to find your corrected flow and pressure ratio (aka. you x and y coordinates on your compressor map).

Go BorgWarner.......It's not like I work there!!

 

here is an older thread that has some reference to the weak shaft/bearing

https://ls1tech.com/forums/forced-induction/567290-twin-gt40-s-single-gt55-91mm.html

 

if that is true then fi-x unit it is...or precision...dr.turbo any suggestions for my setup/goals? I'd like full spool up by 4k if thats possible

 

FI-91X would do that with a 1.1A/R my friend. The GT55 has been a little suspect on some setups in the past indeed. We like them though and we carry them and sell them to many customers. Yes some fail, but so do ALL the turbo manufactures at some point. If it was my personal car I would go bigger if your going all out.....lol

 

how much bigger in physical size is the fi94x compared to the fi91x? Like I said need to fit it where the battery was without any cutting.

 

GT55, FI-91X, FI-94X or EZ-94X billet are all the same basic size. The billet 94X and GT55 maybe about .5" shorter.