FCR zip-tie mod/accel pump problem?

So I was jetting my 06 yfz450 yesterday and decided to do the zip Ty mod despite the fact that the pump was timined fine and had 0 lag I wanted to make sure it stays like that. Well my question comes from the fact that I went and looked at the pump on my 04 yz450f and it seems to lag A LOT. It responds instantly but when i WOT quickly it falls behind. It sounds like I can hear the plunger too. Like it's moving along an old piece of rubber. I've never had a problem with it bogging as 1/2 throttle is all I ever really need but I did the zip ty mod to it and it sped it up a lot but towards the end of the stroke it seems to slow down. Is this a worn out part? Is it just less timing on the bike? I think I could get by without it really but at the track I don't want it to bog on the face of a fat jump. So is it stock timing or should I replace some stuff down there?

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