Hi @ptrblck thank you for the reply. I solved it by moving this line  torch.matmul(alpha, params_dicts[f"layer_{i}"]["eign_vector"])  inside the for loop. so the update code is;
def new_model(x): # x represents batch images.
    # print(x.shape)
    for i, old_param in enumerate(model.parameters()):
        weight = torch.matmul(alphas[i], params_dicts[f"layer_{i}"]["eign_vector"])
        x = func.linear(x, old_param + weight)
    
    return x