Loss of power

[Weenies3]

I need some serious help. We just replaced 89 Toyota 4x4 with new head gasket, fuel filter, timing chain and cover and a new exhaust system. Now we're getting no power especially trying to go up small hills. Could someone please help me!! Also we hear an exhaust leak coming from the manifold could that be part of the problem? Any help on this matter would be greatly appreciated. I'm definately a dummy when it comes to mechanical work.

Thanks
Weenies3

[Castis]

it could be an exhaust leak. it could be the timing, even if its off one link. did you torque all the bolts on the rocker assembly to 35(?) ftlbs?