After all this talk, I decided to do an FTP test on the turbo for giggles last night! Came out with an estimated FTP of 327W.
Since my last estimate/measurement (332W) was taken from a 25 mile TT on the road (I have actually put out up to 337W in a 25TT but not routinely), this test on the turbo seems to suggest I have improved, taking into account my power on the turbo is always notably lower than the on the road (i.e. much more than 5W lower).
My 5 minute blowout was a turbo PB as well at 417W
