More than likely a Metro mod as just about every 135 delivered in the US was completed by them rather than AHI.
Single Pilot IFR Avionics Installation Kit PN 135M-I50 and I35M-250 installed by Metro Aviation, Inc. in the ECI35 helicopter.
EQUIPMENT MAINTENANCE MANUAL
SINGLE PILOT IFR AVIONICS INSTALLATION
PART I SYSTEM DESCRIPTION
CHAPTER 23
As a requirement for IFR the GPS system requires forced air cooling for the GPS/NAV/COM System.
A supplemental avionics fan is installed to provide this as well as for the transponder for added reliability.