For reference, you can look at the Chevrolet Omega 4.1L that was made in Brazil. A modernized Chevrolet 250 with MPFI. 166 HP at 4500 RPM and 250 lb-ft at 3500 RPM. Gas mileage around 25 MPG. Years 1986 to 1998. The MPFI solved the fuel efficiency problems of the Siamese port. I guess this could be considered the ultimate improvement to a Chevy I6 negating turbocharging (another story). The last time I searched for info, the new designed aluminum cylinder head for the 4.1L had leaking problems. In my opinion, they stopped I6 engine production because there were other more reliable (also probably cheaper) engines available at the time.
It takes a ton of $$$, research and testing to develop reliable fuel systems for engines. Manufacturers of add-on EFI kits do not have the resources that the major automobile manufacturers have. So, I wouldn't be surprised to hear that some Holley (and other companies) EFI kits fail. For example, kits for a Chevy 350 V8s have failed because of faulty capacitors. Heat (typically exhaust manifold), noise spikes from a 12Vdc power source, need for consistent fuel supply (some new 12Vdc pumps fail), wear, on-and-on, are some of the headaches to deal with. Then there is the need to be proficient in setting up the EFI system parameters by computer. A trial-and-error process and if plug-n-play, still need tweaking. To make matters worse, it usually happens that things fail when you are furthest away from home. In that case you need to take all your troubleshooting equipment with you as well as spare parts.
Until enough poor souls have plowed their way forward to creating reliability and can provide empirical information to ease the installation and setup for the rest of us, I'm going to stay with a humble carburetor.
