06 225 pro xs surging/bucking at wot. ideas?

[deception]

culprit=06 225 pro xs
don has been helping me with this problem. im in ky and the closest mast mechanic i can locate is all the way up past cinci, oh. ok this is the info so everyone can brainstorm and tell me if they have had simular problems.
boat takes off like a bat out of h=ll, very strong like new. after approximatly .75-1mile down lake it starts to back off of the wot speed, and starts (surging/bucking), now at this point if i ease off the hot foot it will hold at 5000 or so rpm @57-59mph. keep running and it goes to 55mph and holds. here is where it gets interesting. if i start trimming the motor DOWN it gets alot worse, (like riding a wild bronco worse), start to trim up and it starts running better but never back to wot. NOW, if i stop for just 5 seconds, i can take off and have that power back, get to wot and (repeat). here is what i have replaced.
1. primer bulb and hoses.
2. gas tank is ok.
3. pulse fuel pump kit
4. new fuel filter
5. new spark plugs
6. battery cables checked.
7. no horn or guardian beeps
*note, started after i changed fuel filter/spark plugs and pumped old primer bulb. this tank of gas was first with quickleen. while changing primer bulb noticed gas line was flaking (thought this was the problem) changed line and bulb. have not taken of vst and inspected yet.
im puzzled that when i trim down it gets worse. any ideas as to what looses fuel with the motor in that position. im also curious if i damaged a plug wire when changing them, is there anyway a plug wire could cause these issues or is it extreemly unlikley. anyway, im learning alot and enjoy the post and brainstorming.
i will try any ideas and post results.

[Largemouthlou]

anti sipon ball or venting problem??? Ck tank for any debris that may get caught up in screen, shoot a little compressed air back through fuel line into tank. Tank will presurise a little so hold fingure over hose till it depressurizes or it will shoot gas back out..

[EuropeanAM]

You could have debris in the VST, that is getting into the inlet(s) for the high pressure fuel pump when the engine is trimmed "down" (the High Pressure pump is at the VERY BACK of the VST, so this "at least makes sense".

[redline]

Try running it on a portable tank....I know you said fuel tank was "ok", but it still may not be. Sounds as though there is a lack of fuel volume, since your problem once brought back down to idle and then will take off fine..The VST has a chance to fill back up. One reason for the trim angle issue may simply have to do with the fuel level within the VST and the feed to the pumps. If it isn't full, the motor angle may provide "some" fuel at certain angles and not others. Eliminate the on-board set-up as a possible problem. If it goes away you know where to look. After that you still have a problem, look into the VST for debris {+1 Don}.....one other thing.....just when it starts to surge....have your buddy prime the bulb.....see if there is a response. A word of caution though....DO NOT run it in the surge mode for too long....meaning ONLY A SECOND or TWO.....you could melt a piston.....

[Flipping57]

What size fuel line did you use when you replaced it?

[deception]

ok, tommorow i am going to do the following. check the vst. i am thinking that if i am very careful i can take the top of it off. i know there is a seal under the top cap. i will check for trash that may be in it. if nothing is found, i will pull the gas tank housing off so i can access the tank (triton boat). then i will attempt to remove the entire valve assembly that is screwed into the tank. i only went as far as the anti siphon valve, so anyone who has info on how to remove the entire elbow assembly on a triton please reply. as for the hose size i used when i replaced the old one, it was the same inside diameter. i dont recall the ID, but i checked with don so i know i got the right ID mercury hose. i will post the results and try everyones ideas one by one.