• How can I improve frame rate?
GPL has just plain amazing graphic quality. The best bet to improve performance is to upgrade your computer, (see Requirements above), however, for many people a computer upgrade might not be an option right now. GPL does have a good variety of graphics options, allowing different levels of detail which can help with framerate. Again, the manual and Strategy Guide do a great job providing information on getting the best framerate within the game. What I'll do here is list the options available to you and briefly explain what they do. One bit of advice, start with minimal graphics level that produces a good framerate, then try to add textures or objects from there. Similar to car setups, try each option one at a time. If you add a bunch of different graphics at once and your framerate slows down you can't be sure which is making the framerate slow.
Features: Turning each of the features on displays texture on each object to increase the realism. When turned off the object will be displayed with one solid color. The features option gives you two choices for displaying the textures, ahead (A column) and in the mirror (M column). The A column let's you choose which textures you'll view out the front and sides of the car while driving while the M column let's you choose what textures we'll be displayed in the mirrors.
Quality: Quality is simply what it says. Three image enhancing effects are available here, Anti-Aliasing, Dynamic Lighting and Specular Highlights. If you have a low end computer you're probably better off leaving these off.
Effects: The effects are graphics created by the cars. Engines can catch fire or smoke, tires will smoke when grip is lost and leave skid marks on the track, cars will kick up dirt and dust when leaving the track surface. Great detail here, but all take up a significant amount of system resources.
Detail Bias: Detail bias is the distance ahead which you can see graphic details. With the indicator moved to the right (+) you can see details farther away, moving it towards the left (-) decreases the distance you see detail.
3D Accelerator: If you have a Rendition or 3Dfx card this option tells the game to use that card. The third option, Software, is for those without a graphics accelerator card. If you don't, it's strongly suggested you look into purchasing one.
Resolution: Seven different screen resolutions are available with the v1.2 patch, from lowest to highest they are 512X384, 640X480, 800X600, 960X720, 1024X768, 1280X1024 and 1600X1200. If you have 3Dfx' Voodoo2 equipment, the best you can hope for is 1024X768 with two 12MB boards SLIed, but Voodoo3 and TNT Ultra cards support resolutions up to 1200X1600 or higher.
Mirror Detail: This option lets you choose how much is displayed in the mirrors while driving. Full will display all objects and uses the most resources. From there you can choose Cars and Track or just Cars. One tip, if you choose the latter two take this precaution first. Change the mirrors to full, then uncheck all the M column items in the Features section. Then go ahead and choose Cars and Track or just Cars. If you don't, while you won't see the textures in your mirror the game is still writing them, just not displaying them. This can have quite an effect on your system's performance!
A few notes on sound...
One more item that can improve the framerate is the sound which has two options to play with. One is in the options menu. You can increase or decrease the maximum number of sounds heard. The more you hear, the more resources are used. Second is outside the game. In your GPL directory there is a file called app.ini and within it you'll find a line for sound quality. The default value is 2 but you can try both 1 and 0. You'll lose sound quality, but at the same time improve the game's performance.