which route for A4
If you want more cam, the next step up is to consider a 228/228 112 cam. Most tuners can make it pretty streetable, and you may find that this much power is all you need if you are staying on street tires, and you can skip the spray. Heads/cam/headers/converter make a HUGE difference in performance.
While there is no official definition, most Stage 3 heads are not for stock cubes.
You would/will be amazed what a cam/stall does to an LS1.
For strictly street I'm with Ragtop, all that plus nitrous is a LOT of power on the street. You will absolutely want to run drag radials as soon as you put a converter in.When looking at cams that will work well in an auto don't just look at whether the LSA is 112, 114, etc. Look at overlap. LSA is only one factor in determing overlap. Take the duration from any measure point, wehter it be seat to seat, advertised, .05....and apply this formula.
[ (intake duration + exhaust duration) / 4] - LSA, and finally multiply by two.
Overlap is what will determine the idle quality. For reference I daily drive my MS3 with 13.5* of overlap daily and it is not a problem AT ALL. A 224 on a 112 has 0* of overlap. A T-rex has about 25.
(all measured at .050" lift) 

