How is the DME calculating EGT's? Never heard of that before.......how would it even do that?
I would think that adding a probe in the manifold would be the best way to do it.
I don't know the specifics, but it has a model that calculates EGT off a variety of engine parameters in real time. I'm guessing the EGT model in n55 is more sophisticated than n54 since the turbo is controlled based on a compressor characteristics and turbine power table vs just a duty cycle base table. There are models for pressure drops across all components, so the DME (at least n55) likely has estimates for both EGT and preturbine and post turbine back pressure that feed into the turbine power calculation. The models are probably very accurate in a stock configuration, but accuracy will start to diverge as more mods are made, and the corresponding tables aren't adjusted accordingly.
With a larger turbo and better flowing manifold, I'd wager that actual EGT are lower than predicted by the model, due to pre-turbine back pressure being much lower (unless those tables were known and adjusted accordingly).
OP, since your manifold has two bungs, I think it would be awesome to put an EGT in one, and a pressure transducer line in the other! The challenge would be integrating with car to log through MHD; that's well outside my wheel house. I think perhaps Reflex with CAN integration could do it?
I hope somebody more software savvy chimes in. Good luck!
