I have a similar setup on my Cougar.
Injen
SVT TB
00 SVT UIM
Stock y-pipe cut and welded
Hi-Flo cat/Dynomax/2.5 pipe exhaust
I know I run too lean at WOT...usually hitting around 0.92V or so. I have an AutoTap and an Apexi to prove it
. The Apexi only seems to be to be partially able to richen up the mixture at WOT.
So, I am going to 19lb injectors and a 73mm C&L MAF calibrated for those injectors. Results yet to be seen but I am using figuring around your idea, where if your starting to hit close to the HP of an SVT engine (192 HP originally), then 19lb injectors become required. Ford would have not spent the extra money for different/larger injectors if they were not required! (trust me I have worked for them)
If you do decide to do 19lb injectors though make sure you either have an MAF/Apexi/Chip (at least two of those). Otherwise your engine will likely run too rich ... loosing HP and blowing away your cat early.
