Which Tiger addon are you using? I looked around for one a while back but never seemed to find a good-quality one for FSX that had realistic flight parameters. The one that came closest had been edited so that the propeller was giving significantly more thrust than it ought to...
I downloaded it from Flightsim.com. It was a repaint of Tim Conrad's AA-5B Tiger. In particular, the one I'm using is aa-5btigerfsx.zip released on 3/19/2011.