OK, I found the needed memory locations to change on the the another forum. Basically, as I mentioned, VWK501 and VWK503 have different memory locations, so the needed addresses to change are:
VWK501:
Transponder Keys: 0x020-0x040
Immo Key: 0x072-0x078, 0x07A-0x080, 0x082-0x088 (Split by a FF byte)
Number of Keys: 0x08A-0x08C
Immo Status: 0x08D-0x08F
Immo ID: 0x0A2-0x0CB
SKC: 0x0CC-0x0D1 (rotate bytes, change it to DEC. 1234 = D2 04)
VIN #: 0x0D2-0x0E2
VWK503:
Transponder Keys: 0x070-0x090
Immo Key: 0x0B0-0x0B6, 0x0B8-0x0BE0, x0C0-0x0C6 (Split by a FF byte)
Number of Keys: 0x0C8-0x0CA
Immo Status: 0x0CB-0x0CD
Immo ID: 0x0E0-0x109
SKC: 0x10A-0x10F (rotate bytes, change it to DEC. 1234 = D2 04)
VIN #: 0x110-0x120
I changed the data accordingly and voila, no more flashing immo led