GA LTT DEVIATION FROM CLRNC ROUTE.

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ON CLBOUT OF HOUSTON HOBBY ARPT ON AN IFR FLT PLAN TO MEXICO CITY; WE REQUESTED A DIFFERENT ROUTING RIGHT AFTER TKOF WHICH WAS B1 TO TAMPICO. CENTER APPROVED THIS CHANGE AND GAVE US A TURN TO INTERCEPT THE BEARING S OF THE GALVESTON NDB. MY COPLT GAVE ME THE OUTBND BEARING OF 205 DEG UPON WHICH WE INTERCEPTED AND PROCEEDED OUTBND. SHORTLY THEREAFTER; CENTER CALLED AND GAVE US A LEFT TURN TO REINTERCEPT. I EXPLAINED ALL OF OUR RADIO INDICATIONS SHOWED US ON COURSE TO WHICH HE SAID HE SHOWED US OVER 45 MI W OF COURSE. HE THEN HANDED US OFF TO ANOTHER CTLR. UPON TALKING TO THIS CTLR; I ASKED HIM TO VERIFY THAT WE WERE INDEED OFF COURSE AND HE SAID WE WERE. I ASKED HIM TO CONFIRM THAT HE SHOWED US NOT ON THE 205 DEG BEARING AND HE SAID THAT WAS INDEED WHAT WE WERE ON BUT THAT THE AIRWAY WAS THE 183 DEG BEARING OFF OF GALVESTON. UPON HEARING THIS; I TOOK THE CHART FROM THE COPLT AND SAW THAT HE HAD INDEED GIVEN ME THE WRONG RADIAL. WHAT HE HAD DONE WAS GIVEN ME THE INBND RADIAL TO THE TAMPICO VOR. I BELIEVE THAT WE WERE THE ONLY ACFT IN THE AREA AT THE TIME; SO IT SEEMED LIKE THERE WAS NO CONFLICT. HOWEVER; IN CONGESTED AIRSPACE; THIS TYPE ERROR COULD PROVE TO BE VERY DANGEROUS. I THINK IF I HAD 1) NOT REQUESTED A ROUTING CHANGE SO SHORTLY AFTER TKOF AND 2) DOUBLE CHKED MY COPLT'S ASSESSMENT OF THE ROUTE; THIS ERROR WOULD NOT HAVE OCCURRED.