I am pretty sure it is. (I tested it with a blink led set to pause 2000 and it was a 2 second gap...well two Mississippis by my count. I spent a while trying to figure out the OSCCON) My understanding of it is that because the pulsein is "narrower" than when the osc is running at 4mhz the timings for reading IR signals is different.so "if stx<760" actually should be a different value. I am trying to understand the maths of what that value should be.
p.s. I know there is a typo in the code portb.4 is incorrect and I have corrected it in my actual code.