Originally Posted by Shocky
The performance looks spot on, 3dmark is a stress test so it's not meant to run perfectly but still on the Galaxy S4 it should be fairly smooth. A score of anything between 10800 to 11800 is normal for the Galaxy S4 so your a bit on the lower end but it's okay, also MDM is the latest firmware for the UK so that's fine.
I see what you mean about Cubed Rally Redline, it's pretty basic but both games seem smooth here, I can't see any lag at all and I'm definitely not getting an lag when playing video files or browsing the web.
I'm using an updated firmware not yet available in the UK but it shouldn't make this kind of difference so I suspect there's an issue with your phone. I would try a factory reset first to see if that helps but if your still noticing general lag or stuttering in games and apps for no reason it looks like you need a replacement.
I would be very reluctant to put another sdcard in that phone, the sdcard issue is probably related.
Thanks Shocky. Well I think I've decided that since a factory reset is a bit of a pain in the bum, especially after getting everything just how I like it, I might as well at least start fresh with a new S4.
My plan is to order another one tomorrow, keep my fingers crossed and return my current one for a full refund when the new one turns up and return the Samsung SD card in the meantime.