Acceleration issue?

[Koop_G]

(Sorry in advance if this is posted somewhere I tried looking) I have a 97 Chevy k1500 350 vortec and I’m having an odd acceleration issue mainly more then half throttle, it accelerates seemingly fine then suddenly feels like it gets a big power boost and starts accelerating as it should in working order. It genuinely seems as it’s getting an extra 30 horse to the ground lol I’m not sure as to why it’s doing this if anyone has any idea or can point me in the right direction that’d be great, I’ve recently had the whole distributor replaced (timing is fine idles at about 650-700 when warmed up) plugs and wires earlier this year (middle of summer) the truck is stock other than the exhaust being catless and a ***** purple muffler instead of the factory one. Any info will help thanks

 

[Schurkey]

Connect a scan tool, verify ALL the sensors especially the TPS and MAP sensors, and all the computer outputs including spark advance, and EGR.

My Monte Carlo does this, more-or-less. I suspect that the computer tuning doesn't allow power enrichment until the engine has been under load for a few seconds.