Thanks Guys!
For some reason my 13F1320 seems to have a problem so I can not see what the math is doing yet with an ICD compile. The MAX232 works fine until I connect it to pin 9, the TX and then it stops talking! As for measuring I am using one of the greatest devices ever produced, The Saleae Logic Analyzer! I can see all the Memsic 2125 values change with temperature so I do not have 1 or more "fixed" values to use. The "duty cycle" value seems affect the accuracy more than the pulse widths. The duty cycle value varies from 498 to 504 which then gets worse when using the look up tables! Just a couple of degrees of room temperature change seems to make a big difference.