my bud Lester has one, I'll see where he got it, you mean the tool that allows
you to remove the fuel lines and AC lines???
IMO if the problem is only when you use the 87 octane MPG tune, try the
87 performance tune and see if it does not do it. If it does not, could be
something in the fuel pump or a minor glitch in the program/computer...
For example (purely speculating here) the fuel pressure is turned down
during MPG mode, and in certain cases, the pressure drops below what
the computer expects to see, could be the sensor's low end is not what
it should be or the pressure is actually too low, or the fuel pump does not
like to run at those low settings... remember, the returnless system cuts
pump voltage to regulate flow/pressure and your pump might not like that!
I'm not saying the tune
is bad by any means, but maybe the factory
components are not quite up to par and cannot handle what is asked of them.
We see it all the time where they cannot handle our highest expectations,
but in this case they maybe cannot handle the
lower demand settings the tune requires for more mileage