I can share some data but nothing formal with my N55.
My coolant temperature went from ~253*F after a session to 205*F with the ETS 5" intercooler (track conditions: sunny/humid, 90-100*F). Measured via the readout on my BMW Performance electric steering V2.
In terms of feel; I had no overheating with the stock intercooler but the throttle responsiveness would taper off throughout the session. It wasn't too bad because the intercooler has time to partially recover on the long straightaways at the tracks I visit, but it was there. The responsiveness is noticeably better with the ETS intercooler; I've yet to have it heatsoak to the point where I notice lag. It was a nice upgrade.
2011 BMW 335i E92 - Le Mans Blue, 6MT, M Sport. JRZ RS Pro, Quaife LSD, BMW Perf Exhaust
Last edited by CJ421; 10-27-2012 at 02:34 PM.