I have done an engine overhaul of my Toyota corolla 160i 2002 sedan 4AFE and the timing is right, the problem is the car it starts nicely but when it moving and accelerate it it lose power. Help plz.

SOURCE: I have replaced a cylinder head of my Toyota corolla 160i 2002 sedan model and put new gasket but it's still mixing water with oil, I need help plz

If the new gasket is the correct gasket type and sized and the head is torqued down correctly, and the replacement head is a used head, it was cleaned and dye penatrent checked for cracks.
And presuming the coolant connection and water pump connections to the block have been check thoroughly for leaking into block (by poor or worn connections. Then the only logical answer is that you have a cracked engine block. You can purchase a dye to put into the coolant to trace where the coolant is leaking into or out of the block. If the engine runs and there is no white smoke out the exhaust, then the leak is not in the combustion chamber (cylinder, piston or valve area of head). Leaks can occur to the oil pan from the water pump connections at the front of the engine block. If you do not want to go through the work of finding the leak. pick up a good condition entire engine from a wrecker and swap the engine out.