boost is low.. so i think..

Ok i just recently started driving my stock GST. when i would drive normally the boost gauge would get to the dash around the middle and usually stays there until shift or give it more gas. but recently it would just get near the middle of the first and second while driving normaly... what could be the problem.
Thanks for the help...

Well your problem would be a boost leak... Time to give it a boost leak test and also get a better boost gauge. The stock ones are very inaccurate and should be replaced with a better aftermarket one.