I have combo Volts/Amps and Pressure/Temp gages in my -4. Both are EI and have performed flawlessly for 15 years. I have slowly swapped out all my non-EI stuff to EI. It works, it lasts, includes good documentation, and has strong customer support. That being said, there are lots of good integrated engine monitoring systems on the market, but may be much more work to incorporate into a flying -4.
Good luck,