Perda de energia

Good morning I am new to everyone, and I have a problem, I have an Audi 4 quattro, 2.5tdi V6 engine of 155 hp Automatic change, year enrollment 1.999, it is very old but it does the service to me, the problem is that from a time to this part, when a slope comes does not go up and how much you step on the accelerator less, I have observed that it seems that it does not change in these circumstances of manual or in position 4 do seletor e, a princípio, parece que ele se recupera um pouco, mas depois cai, ele tem 320.000 km. Mas eu estava indo muito bem até recentemente, para mim é
importante flor e óleo e troca automática filtro