We (me and racin) have done this exact same thing and ran into the same problem.
On the intake manifold where it bolts to the head there are some small pin sized holes. They go through to the injector and the normal obd2 injectors seal it off, the si ones do not. Take your manifold off and JB weld the holes. Just use enough to fill the holes and scrape the rest off.
That should solve your problem
Good Luck
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Gracie Barra Clearwater
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