This fix will let you turn texture caching back on (which you cant do in the standard video options/graphics options. Mainly im posting this so i dont have to explain this to all of my friends that need to fix the lag. So here we go.
Go to your Gamersfirst/APB reloaded/APBGame/Config folder, now look for the config file named APBMachineOptions (Make sure its the APBMachineOptions, not DefaultMachineOptions.) and add this to the bottom with a blank line between the stuff that is already there, and the new stuff.
bCompressDiffuseLocalPlayerCharacterTextures=true
bCompressDiffuseLocalPlayerVehicleTextures=true
bCompressDiffuseOtherPlayerCharacterTextures=true
bCompressDiffuseOtherPlayerVehicleTextures=true
bCompressNormalTextures=true
If you dont know, basically all this does is make it so you dont have to constantly 24/7 be reloading every texture over and over again.
Before I used this, turning my screen around caused HUGE drops in FPS.. and driving at full speed was almost impossible. This also makes combat easier because your PC can focus more on the bullets flying all over the place. I have tried what other people have suggested like turning off dynamic shadows and bloom in a config file, but that didnt help at all. Good luck everyone! (P.S. if you are enforcer i suggest not doing this so i can own you in game.)