k1200RS loses power - any seducetions?

[(RIP) Bin Ridin]

Hi,
Buddy here has a low mileage '04 k1200rs which was left unstarted for 2 years....it was in the heat although under shade and wrapped up.
Starts and runs ok, but has lost power on a few occasions leaving him limping home.
Dealer changed the fuel pump, no difference.
No more details than that at present, but I wonder if anyone has run into the issue?
Ta,
Bin

 

[(RIP) Bin Ridin]

Bump?

 

[(RIP) Kaister]

i'm assuming a complete fuel drain and refill has been done ?

 

[(RIP) Bin Ridin]

Yep, that and the fuel pump. Fuel Pressure Regulator was in my mind, but only guessing.

Any clues?