I can't comment on the C.A.T.S. But I'm running the EBL Flash with the port mod and like it. With the port mod I'm running 98% of the original harness with the exception of the spliced-in port injector harnesses. I also had to install a high pressure fuel pump for the port injectors. Of course if you stay with TBI, no wiring mods would be required.
There is no doubt that the standard EBL flash will enable the tuning of TBI on the 400. But you will also need to supply enough fuel and air for it. Give some more information on the engine, cam, heads, etc. And post your specific questions or concerns.

 

Thank you ladreamer. the engine is .40 over with a mild performance street kit with 5.7 rods, Hypereutectic pistons, Hi volume oil pump. The compression should be around 10 to 1. I am planning on using the 58cc 305 heads for the time being. I kept the cam mild 224/224@50 465 lift 112 lobe sep. As for the my specific question it really only is if I am heading in the right direction with the EBL flash. I have done lots of reading on chip burning through the forum and other sites. Lots of information to absorb. But the EBL seems like a no brainer to go with. Thank you