Rejet problems

[vaper]

So i gave my mechanic a K&n lunchbox and a rejet kit. He rang me 3 hours later saying he wants to put the stock airbox on because it has gone way down hill on the dyno before a rejet. He said it gained some power at 4500 rpm but is dangerously lean drops tremendously and he doesnt think a rejet can help it. Any advice ?

[Paulcet]

Advice:  Get a new "mechanic".

[craigs449]

Advice:  Get a new "mechanic".

HAHA ^^^^^^^ +1