Stutter when playback - fsrecorder

With PMDG's MD 11, I get 30-35 fps (locked 35) at OMDB flytampa with 100% traffic (WOAI). But when playback, the stutter is intimidating. I have visited its site and done all the suggestions given, such as unchecked radio com in user aircraft, set to 1/4, and also unchecked almost all boxes for traffic ( except engine on/off, gear and flaps), I only got 18-20 fps when playback without stutter; which I thought it was normal, but some people who have similar systems to mine said it shouldn't have affected that much on the fps. I own a low-medium end system, could it be the problem? Tell me whether this is normal thus I'll stop complaining before I'm humiliating myself. Thank youRegards,PrabowoAMD X2 250 Dual Core 3.0 GhzGeforce 9800GT 1GB4 GB RAM500 GB HDXP SP3