Can I change PCIe TLP's Tag value?

Hello all, We are doing a test by modiying a simple PCIe device driver to do memory write and read. Write and read from to the device's PCIe core's internal register is ok but when we do memory write and read for the device's internal memory, the writes are ok (we can observer the result using jtag debugger) but the MemRd causes error (we checked using PCIe test equipment called VIAVI). The equipment support person said the error came out because the Tag value of the MemRd TLP is the same as the MemWr TLP's. So is there a method by which I can change the Tag value of the TLP? Thank you. Chan Kim