SeaDoo problem.?

[Drew M]

I have a 95 seedoo gtx and about and last summer when you gave it throtle it would jump up and then go down to alittle above idle. we tried everthing from cleaning the carborator and changing the fuel filter. nothing seemed to work untill we switched it to reserved instead of normal where it would take all the gas and not leave a reserve tank. and it work fine like nothing was wrong. now this summer we took them out again today still useing the reserve and it started acting up again. any ideas on what it could be. fuel pump, fuel lines, other fuel filters? i have no clue and none of the seadoo dealers will servise them because of there age.