Gaming Build for GTA IV

First of all, what you need to know is. He will need a fast quad core, and a fast SINGLE GPU. GTA4 won't even load on a Xfire or SLI setup.

yeah i heard that gta is highly cpu intensive game but is there any change after ultra graphics mods?

It depends on your friends resolution. Because you can't use more than one GPU, playing at higher resolutions and specifically the amount of VRAM can negatively affect gaming performance.

Best choice is a fast 4 core processor and the best single GPU he can buy.

resolution is 1080p native.looks like in this also,2500k is the best cpu.will that do good even after mods and stuff?

It really depends on the mods. This is where you're going to have to do some independent research. Some mods are poorly coded and are resource hogs. Others, not so much.

Mods will eat up alot of RAM(the regular kind) and more importantly alot of VRAM.

Research your mods, pick out the best video card your friend can afford. Keep in mind since he's upgrading his CPU, this will most likely require a RAM upgrade and of course a motherboard upgrade. This will eat up a significant portion of his budget.

Also note, the next GTA is due out this fall... seems a waste to build a system around a game that's about to be replaced.