Hi Ken,

I may have a solution to your problem, or part of a solution...

I picked up a PING module the other day and did some playing and watched the last video you posted very close.

My conclusion is you need to run the PIC at 20MHz.
I am running a very basic code to calculate distance so my findings may not be a total solution.

Watching the video it appears the car is pointing more at the corner the first time through, and the second time when it does not hit the wall it is just a bit to the right and a little more straight on. When I try corner targets the reading becomes very erratic. Maybe for you have the front sensor pivot slightly from left to right. Could be done with a spring and a cam bumping on the wheels?

Back to the software. I am using a PIC running a 20MHz.
When I set the PULSOUT at 10 giving the 20us you have in your code the readings become inaccurate with a great deal of fluctuation and slow to respond.

When I set the PULSOUT at 2 giving a 4us pulse the accuracy is within an inch and very very quick to respond.