Holley Sniper EFI review after 10,000 miles on my 1967 Corvette: it works, with caveats.

The self-learning tune sorted itself out within about 200 miles. Cold starts went from a choke-and-warm-up ritual to turning the key and driving. Hot restarts — historically terrible on a carbureted V8 on a hot day — became immediate. Fuel economy improved by about 15%.

The downsides: the Sniper's wideband oxygen sensor placement matters a lot, and the stock location isn't ideal on a big-block. I ended up having a bung welded further downstream. The handheld controller is also clunky — the app is better. Not a perfect product but a genuinely functional one.