I have an annoying little problem with laptop serial comms. I'm sure it was never a problem before, but it is now. (I have a slightly different, but related problem on standard ECU'd Imprezas too, so it's not all the fault of VEMS)
When I connect the laptop to the ECU all is well when the laptop is running on internal batteries. (When the laptop is not connected at all, all is well too, but that's what anyone would expect...)
However, when I use my 12v to 20v boost converter (bought from Maplin) to power the laptop, the CLT jumps straight to 101C (but sometimes drops back a few degrees briefly) and the IAT jumps up by 10 degrees or so. Other sensors may be affected, but I haven't looked that hard.
I'm sure this didn't happen before the car doors (where the fag lighter socket is) were retrimmed & the wiring in them repaired. But then there's no accounting for TVR wiring!!
Any bright ideas as to how to stop this? Short of optoisolating or making the serial port into a bluetooth port, I am out of ideas - A perfect ground plane for the whole car is just not going to happen...
Sounds like a good time to look at these:
http://www.brainboxes.com/product/bluetooth/BL-730.aspx