K04 vs. RS4 K04... Just read in a an article that they are not the same...
 

The K04 flows 11% more air over the stock K03, and the RS4 K04 flows over 34-38% more air over the stock K03.(according to Eurotuner Mag) The car was the black RPI GTI. It said most upgrades do not use the RS4 K04. Anyone experiment with the RS4 K04? How much safe Hp can I squeeze out of a K04 upgrade? (RS4 or Regular K04)

Yes people have tried to use the RS4 K04 and it does not work with
 

any standard K04-15 chips. The RS4 K04 is not a bolt on turbo since the bolt pattern for the exhaust side is different.

You can get 250-255 hp out of the standard K04-15 but to do so you will have to run it at 27psi of boost which puts it at its CFM limit.

I beg to differ.....I drove a '99 Passat with the RS4 KO4 and it works.......
 

some changes to exhaust side and programming from Juan @Werks of Art (GIAC). Other mods incl. adjustable FPR, FMIC, larger injectors, Brullen exhaust, plugs...... the usual.
Car pulls really nice and is oh so smooth, lag is just a bit more than stock.
HP, best guess approx. 260 - 280 depending final tuning.

how come the RS4 K04 doesn't work?

One idea that's been toyed with (but not enough to release).....
 

is using a K04-15 with a 16 impeller. A "hybrid" K04 mix, standard bolt up patterns, with an increased cfm rating.

This one?
 

He's putting down 173whp. That's a long way from 260bhp. However, I wish him luck in tuning it.<ul><li><a href="http://www.clubb5.com/forums/viewtopic.php?t=52486&amp;sid=114df25cc44af2293aa3 fa3e75628a22">http://www.clubb5.com/forums/viewtopic.php?t=52486&amp;sid=114df25cc44af2293aa3 fa3e75628a22</a</li></ul>

Running 173 before adding the RS4 K04

Just saw that, good call.