I've never considered a tune when I did my M50 manifold mod on my S52.
After the installation, I noticed a loss of torque down low, but I gained it all back on the top end! Great bang for buck imo, even w/o a tune
98 M3 Sedan
06 Yamaha R6 (SOLD)
04 Honda Civic (Beater)
93 318i (SOLD)