GM had windshield antennas in the early 70's, and they didn't work terribly well for them either........
The 944 system has 2 main vulnerabilities;
The factory signal booster can quit working, &
The ribbon leads coming out of the windshield can fail
(check around the PS cowl area to see if they have broken)
I've purchased an internally amplified '968' style antenna, but have yet to play with mounting options. I'm thinking of securing it in the hatch area to see how it works, as I'm opposed to drilling any holes in the car.....even though that's what they did on the roof of the 968's
Brian