Seat Alhambra - losing power?

My 1999 Seat Alhambra is losing power. 12 months ago, I got a new air flow meter and that seemed to solve the problem. However, when I accelerate, eg, going up hill, the engine just loses power and then slows me down.
I have had a look under the bonnet, and there seems to be a lead (near to the air flow meter), which isn't attached to anything. I can't tell where it has come lose from. I have taken a photo. Not sure if I can upload photos on here. Thank you x