There are a lot of sites that list 1/4 mile times. I'm sure you can find a time slip from both an STi and R with all the deets. It'll give the story of who would win on what type of race well enough if its broken down properly.
That being said and without looking any further, stock vs. stock, STi everyday, all day.
JUST a tune, that'll be a driver race.
Modded stock turbo and a tune, back to the STi.
Even with the EA113 K04 fsi, the hardware on the STi is seriously more beastly with a good size larger snail. Its also not substantially lighter.
And the K04 you're talking about is what comes on the R.
To be honest, you've highlighted one of the main reasons i dropped my golf R deposit and picked up a great deal on an A3q 2.0t with the EA888 once i made the connection (TFSI, not FSI for those who may not know). The FSI in the Golf R isn't much more than an EA113 1.8t from the MKiv's with a seriously updated head and direct injection. Its the same basic architecture. The EA888 2.0t TSI is an all new motor which is beefier in base trim (which the R model is not the base trim, uprated internals and such) and much more capable. The TSI will gain a lot more hp from the k04. Not to mention much more reliable.
Come to think of it, though, this means you've posted in the wrong forum, ooops! The giant TSI on the engine cover and in all their propaganda is bull****, its an fsi.