if there is a leak it will cause a noticable difference, i don't know how much loss in power has accrued but it could be down to a leak somewhere...you'll be surprised how such as small leak in the engine can cause such a noticeable difference, i have a leak between my mani and head and it drives like crap lol. i would just double, double check every vac and pressure line, jubilee, t piece you have. maybe right a list of all the potential causes and do an elimination thing one by one till you find what is causing it.