I had the same problem and couldn't even use any mods other than lcpdfr. I did a little research online an added a Command line to my gta 4 directory and BAM! fixed it. My gta resource went from 200/120 or something similar to 250/1700
Open notepad and add this, then save it to your gta directory as commandline
-renderquality 0 -shadowdensity 0 -texturequality 0 -viewdistance 0 -detailquality 0 -norestrictions -width 800 -height 600 -availablevidmem 12.0 -percentvidmem 100 -DX9 /low -renderquality 0 -frameLimit 0 -nomemrestrict -noprecache -minspecaudio -safemode