Need help!
It's likely the front o2 has insufficient switching due to the relocating of the o2 sensor in "cooler" exhaust stream
As for the tune, give it about 200 miles to adjust, and evaluate the car then, most don't need a tune, but some do
BTW you can usually get a few more horses with a tune, but it's not required (usually) if you plan on more mods (heads, cam, etc) you may want to hold off on a tune untill you get into more intensive mods

