talbot express 2.5 turbo diesel low power?

i have a 1989 2.5 turbo diesel that is lacking power (50mph top speed) while checking that the turbo was actually running i noticed that two rubber pipes have been cut and blanked off.these pipes go to a small valve on the back of the fuel pump similiar to the valve on the waste gate, should these pipes be connected to the turbo somehow? and is this why i have a loss of power? can somebody please help me on this. thanks