TBI and EFI if it uses a MAP (Manifold Air Pressure) aka vacuum sensor are limited in their sensitivity. Hot EFI set ups as found on the Corvette and Camaro use a MAF (Mass Air Flow) sensor to measure the volume of air being sucked into the motor to calculate the time setting for the injectors to stay open. If you use a long duration cam with a TBI it thinks you are running at WOT while the motor is actually at idle and dumps in way too much fuel due to low manifold vacuum due to a long duration cam. A EFI or TBI cam usually has an LSA of 114-116 degrees. A hot carburetor can will have an LSA of 108 or 110 degrees. (Oh as I read what I just wrote I forgot another sensor used by both TBI and EFI rely on: a throttle position sensor (TPS), that tells the computer if you foot is in it or not, or if the car is at idle, or anywhere in between).
Shortening the LSA increases the amount of overlap which means both valves are off the seat at the same time for a longer period of time. This plays all (nether region) with the MAP sensor and confuses the computer which is being told one thing by the MAP sensor and another by the Oxygen sensor and yet a third by the TPS. (hot EFI cars also rely upon a wide band oxygen sensor that can more accurately measure the amount of oxygen that has gone through the motor without combining with a carbon atom), than the older narrow band oxygen sensors do.
You are restricted to very few if any cams other than stock TBI profiles with a TBI set up. You can look on the cam pages in the catalog and look for a grind that works with a TBI and then compare that grind to a carburetor cam. There is no rumpitty rump rough idling cams available for a TBI motor. The computer would roll over and put itself in limp home mode. (think of the commercial with the young mother with her daughter in the their Japanese station wagon crawling down main street a 12 mph with cars behind her honking their horns as she apologizes to them. Then the very young daughter says "^%$(&^@## sensor" to the tech at the service center when the car is finally fixed. That is an example of limp home mode, and the fact that kids pick-up the strangest things!)
Last edited by Big Dave; 10-26-2015 at 10:01 AM.
Reason: thick finger typo removed