I popped the big trim piece off first, and even popped the mirror off its stalk. I still could not reach behind the trim to get that small plastic piece out.
I did not do all that. I loosened (but not removed) the bolts holding the grab handle on. I did not pull any trim/moulding/weatherstripping off of anything. The cable tucked in behind easily and I can't see it.
I ran mine starting from the OBD port and going up. I had plenty of length to spare when I got to the top to plug it into the black box.
@chronorp, maybe you routed the cable under the bottom edge of the lower dash, instead of through it from the side? If you run it through the side, there should be a few more inches of slack for you.