2004 200HP OX66 RPM fluctuations

[M-D]

This is a VX200TLRB
Bought this boat / motor in August of 2019.
Prior to using the boat, I cleaned / replaced all filters, had Brucato flow test and adjust the injectors, cleaned the O2 sensor and barbell (they were not carbed up at all). Last year I eliminated the LP pumps and put in a Holley fuel pump.

In the past, both before and after the Holley fuel pump addition, when on pad and around 2000 RPM I have notice (by sound only) the motor seems to change RPM slightly.
Yesterday while on pad at 3000 RPM I heard that same sound and looked at the tach. RPM's would jump up 400- 500 for a couple of seconds and then back down to 3000. It only did this 3-4 times on a very short run and never did it again the rest of the day.

I have done a search for similar issues on this board and didn't find any results.

Any thoughts on why this is happening?
Anyone have this issue before?

[CJ1]

1st thing I would do is either replace or test the o2 sensor and do a tps sweep test. Cj Cj

[M-D]

THANKS for the response Cj1!
Not sure how to do either, will do a search here, guessing these procedures have been discussed before.

[M-D]

Tonight I did the TPS sweep. Has 0.47 VDC at idle position, smooth transition from idle to WOT position with 4.19 VDC at WOT. I think that is within or right at spec correct? I believe it to be the original TPS with no previous adjustments as that yellow paint on both adjustment screws has never been disturbed.

Something odd while doing the sweep, about a 1/4 way off idle position there was a buzzing type sound coming from (I think) near or at the TPS. It did not last long but did it every time at the same general spot during the sweep.
Removed the O2 sensor and have it, the brass block and the barbell soaking to remove the carbon buildup which was very light.

[Brianmoore25]

Have all battery connections and grounds been removed and thoroughly cleaned? Also a knock sensor going bad can cause similar issues.

[M-D]

Have all battery connections and grounds been removed and thoroughly cleaned? Also a knock sensor going bad can cause similar issues.

I will inspect all connections but pretty certain they are GTG. Didn't realize there is a knock sensor, will look into that...THANKS!

[CJ1]

TPS sounds good. Brian is there anyway to test a detonation sensor? CJ
I wonder if the shift inhibit switch could be doing this. I always unplug them just to be sure.

[Brianmoore25]

Only way I know of is with the old winky Blinky. Can't remember code number off top of my head. The knock sensor is definitely not a common problem.

[M-D]

Got the boat out yesterday on a very small lake so I didn't do much running but I never saw a RPM change on the tach or heard the increase. New plugs and O2 sensor clean. Will update this post if it continues to happen. Thanks again for all the replies!