There are no TSB's on dealerworld and the only experience I have had with that style of noise was an S-10 that had a bad radiator cap. The cap wouldn't seal correctly and allowed air into the system. That air traveled through the heater core and thats where the noise was coming from. Replaced the cap, topped of the system and bingo, no more noise.
2006 LS coupe, manual, Victory Red
Sportlines, FE5 struts, shocks, front swaybar, Progressive 22mm rear swaybar, Airlift load assist rear airbags, TWM ST shifter, smoothed TB, LSJ exhaust, debadged, demudflapped, Yokohama AVID Touring P195/60R15's. Soon to come 17x7 Motegi Tracklight 1.0. Best to date 15.402 at 90mph
"No friend ever served me, and no enemy ever wronged me, whom I have not repaid in full."
Lucius Cornelius Sulla