Aaron,
Thanks for the reply. Output of /var/log/ltm below after copying your text to the irule, ads.imp.
Sep 1 07:37:11 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: 501: Updated URI: /adserver/impression/pid=4/oid=3/rand=%5Btimestamp%5D/?click=
Sep 1 07:37:12 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: New HTTP request to /adserver/impression/pid=4/oid=3/rand=%5Btimestamp%5D/?click=
Sep 1 07:37:12 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: Matched URI check
Sep 1 07:37:12 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: 501: Updated URI: /adserver/impression/pid=4/oid=3/rand=%5Btimestamp%5D/?click=
Sep 1 07:37:13 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: New HTTP request to /adserver/impression/pid=4/oid=3/rand=%5Btimestamp%5D/?click=
Sep 1 07:37:13 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: Matched URI check
Sep 1 07:37:13 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: 501: Updated URI: /adserver/impression/pid=4/oid=3/rand=%5Btimestamp%5D/?click=
Sep 1 07:37:14 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: New HTTP request to /adserver/impression/pid=4/oid=3/rand=%5Btimestamp%5D/?click=
Sep 1 07:37:14 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: Matched URI check
Sep 1 07:37:14 tmm tmm[1128]: Rule ads.imp : 172.16.102.231:1158: 501: Updated URI: /adserver/impression/pid=4/oid=3/rand=%5Btimestamp%5D/?click=