i wouldnt count on tie rods to begin with, but they well maybe due for some new ones. Lets start off simple. Have you had your tires rotated and correct balance weights from a hunter "static" balancer?
The reason why I say this cause my balt had the same exact issue, turned out to be 2.5 ounces overweighted per wheel on the hunter machine...runs like a champ now with hi-low hits, but no vibration atm.
2009 Cobalt LS XFE U74
Mods: K&N Typhoon Intake, Option Cat-Back Exhaust, Cosmo Short shifter, Maxxim Ahead 17X7's, MPx shorty antenna, FE5 Strut/shocks, Tein S Techs, Moog endlinks, Moog spring seaters, ZZP shorty header, LSJ downpipe, LNF front grille