the gtrs, has a flang to fit the stock manifold, and a smaller inlet
the full gt2871, is well, just that... the full turbo is probably good for another 50-75 hp

and... you are running a stock ecu, with gtrs turbo ?... i hope you arent boosting more the 5-7 psi, or you are asking for a blown motor

 

Im tryin to figure out the boost controller at the moment not having too much luck. its a Greddy PRofec B-specII.

 

who sold you this car? not wanting to know his name, just if he was on any audi forums like here, AW, AZ?

keep your boost BELOW 5 psi if the stock injectors are in there. otherwise you're going to lean out the motor.. but yes, mika always tunes for 550cc injectors unless it is tweaked otherwise(which it won't be since it's for an eliminator). but what are you doing to regulate fuel pressure? are you monitering your A/F ratio at all? a couple things you might want to look into.. i don't have any experience with MIKA and i don't ever plan on having any. but you may want to research into it a bit. maybe call up ATP's customer support and chat with them..