variation in boost presure acordig to gauge and performance

[Rain]

hello have been reading your valuable forums and have diagonosed weak actuator spring as problem am i correct turbo boost sometimes gauge 80% sometimes 60% before moving actuator arm by hand not more than 60% have checked all hoses including intercooler no problems found there average mpg 25 have changed spaerk plugs air filter fuel filter dist cap and rotor pipe still looks bit black though maybe irrelevant info one of the forums said if boost not more than 2\3 wastegate not ruled out. if allowing turbo to spool up and then can get to boost to 80 % not cosistently boost not holding after manual manipulation of actuator arm bost considerbley more bout 20% my question really is can this arm be moved manually by hand or not this would lead me to thory of weak spring or not also if diagonis correct does anybody know wher to get one from as not paying 250£ as one forum reader was told have only come to this diagonosis through reading of your forums which i am appreciative of any help now appreciated thank you car is vollo850t5 saloon 96 sedan no fault codes showing either