This happens with a moderate acceleration, if I slowly try and increase it, there's pretty much no response, I have to ask for it moderately to get a response and the response is the sputtering. late-to-the-party powervalve
Before you start all that, just do a fuel-pump volume test ; 1 qt in 1 minute at 500 rpm
This was hard to test because the idle is set higher than 500, but it did seem a little weak so I’m replacing the fuel pump this morning. Luckily it’s fairly easy to get to. Will report back what I find.
