You should 100% verify the tune. Do you let the EFI control timing? Most times I see this on the forum and people end up regretting doing that. Do you know what kind of timing curve it has? That would be the first thing I would check.
Rusty is correct. The default timing table in the Sniper is really basic. Like only three steps in the timing. You need to build a good table to to make it work.
We install a bunch of these in my shop. Currently have a 340 '72 Barracuda now that I'll be tuning this week. The basic fuel and timing table will get it going, but it all needs to be tuned.
