Looking back at your first post and I am still not clear on a few things.
ECU to PC = YES
PIC to PC = YES
ECU to PIC = NO

You may want to look at the PBP manual, I can not find 38400 as a baud rate and 6 is 9600 for SERIN/SEROUT.
o btw the ECU operates at 38400 baud rate thast why theres a 6 there.
Others have talked about using a PIC with an ECU, I have not done so, beyond basic serial com I can not help. So the best I can suggest at this point is to double check the baud rates and if the data is true or inverted.