3.4 swap running very rich

[j.fro]

Looking for some insight here..
The car is a 2000 986S. I've swapped in a 3.4 from a 2000 996. The car fires up and runs well for a couple of minutes, but within 10 minutes, all of the plugs are fouled and it stops running.
The 3.2 ECU has a Softronic flash for the 3.2. that engine ran fine 4 years ago, but died due to intermix.
the 3.4 has new after market fuel injectors (possible culprit), 996 intake manifold, original 3.2 MAF housing and new 124.01 MAF.
thoughts or questions??