[twobjshelbys]

The problem with Cobras and EFI is the exhaust and finding the best location for the O2 sensors. There are many that run them open loop, but if you're going to do that just get a carb. EFI is all about a closed loop controller (really, a servo system with 2nd degree feedback). The problem is that most EFI systems come programmed for an entirely different exhaust system. The O2 sensors are not ideally place with enough downstream pipe to get good averaging, and the lack of a real muffler does not give adequate backpressure to do the averaging. Furthermore, the O2 sensor needs to placed nearly upright, and that is very difficult. Placed in the passenger pipe after the pipes join, at low RPMs there is not enough flow and you get air coming back in that yields an increase in oxygen and the engine will want to run rich. At high RPMs it will probably be OK. The magic is to get your tune set for the exhaust you have. It will take a tuner familiar with your system.

In the end I got a lot more "pleasant" driving experience with my heavy foot at altitude by moving the O2 sensor from the post-collector area to the top of the header on one cylinder.

Mine was the Roush 427IR with the Accel EFI controller. It is way complicated. There are less complicated systems that don't have as many interacting knobs. The biggest problem I had with Accel was getting the altitude compensation set up correctly but once we did that it ran like a champ.