2003 Vauxhall Zafira no turbo

Electrical problem
2003 Vauxhall Zafira Engine Size unknown Wheel Drive Type unknown Manual 54000 miles

I have a zafira with running problems all right on flat but no power on hills had air flow meter fitted bought new valve valve made no difference air flow meter worked for about 5 days then problem came back. To start with when y. Ou turned the ignition off and took the key out it would start after about 2 minutes and problem gone but now that doesn't help now. So think it must be electrical. Have spent a lot of money on this car so would like to keep it. Any suggestions.