Got a 91 rally sport had a V6 engine dropped in a 350 V8 Holley sniper system low end model I think it was the 5150 1 in spacer underneath throttle body. 700r4 & a 274h cam. 3 fuel filters. Sock in tank, frame rail and 10micron at sniper feed. I have the Holly sniper fuel pump 2-in air cleaner and bracket on the sniper that allows the first two barrels to open slightly before the back two barrels running decent gas in it it's a mild build so I put 87 in it sometimes I put 93 octane, 4-speed automatic transmission 342 gears 2800 stall.

this just started happening last couple of days I probably about got about 3,000 mi on the sniper system and it's worked virtually flawless is still in learning mode for some reason maybe I just haven't driven it enough I do a lot of short trips and stuff like that going back and forth to work which is only six and a half miles sometimes the church which is only about seven eight miles, if that. now suddenly when I snap the throttle like if I want to get into it - it stumbles the air fuel ratio goes lean we're talking 20-25 to 1 it only stays there for just a second then it's like the fuel catches back up and it drives decent. at times if I put it in park and snap the throttle it'll lean out to 15 -17:1 for a sec then back down to 13:4 - 14:1.

recently I've seen where it was running about 14:1 and then my idol will go up from 780-830rpm to 850 - 9++. it seems like a vacuum leak to me or possibly fuel starvation which is a fuel filter or possibly the fuel pump trying to go out any advice is very appreciated it's nice running little car. I will update as soon as I can attach video

https://youtu.be/wjWX7fIpFRI?si=bf5f_HlZf9QIiwDN

https://youtube.com/shorts/MOBMnDu1k2Q?si=K2ufCkYUHvtWstD-

 

Sounds like fuel pump on its way out, although there are other things it could be too. I would see if you can verify fuel pressures while driving it and compare to Holley specifications.

 

It will always be learning unless you cal down the learning percentage. You very well could have a faulty injector, which is unfortunately common. Well it's not the injector that's bad but rather the connection at the ECM IIRC. Highly recommend asking here https://forums.holley.com/forum/holley-efi/sniper-efi Make sure you take a log of what's happening and download your config file, and attach both to your initial post. People there are incredibly helpful provided you put in the effort to get them the data they need to identify the problem.