fuel pressure regulator?

As mentioned in a previous post, I am working on my neighbors 2008 Can Am Spyder 990. Still dealing with popping back, poor acceleration. I have replaced the intake boots, spark plugs and wires, fuel pump and oil and filter and air filter. Still seemed to me to have a vacuum leak. With the air box on, when I spray brake cleaner kinda between the carb boots, the idle picks up. If I spray directly at the boots, no significant change, so my next thought was to pinch off vacuum hoses. and when I pinch the hose from either carb, but not both at the same time and remove it from the regulator, popping back stops. Certainly sounds to me like the fuel pressure regulator is the guilty subject, but I would like anyones thought on what else if anything it might be. Thanx again for your help. I would really like to get this thing rideable for at least the second half of the summer. OK My bad. The two vac lines go to the MAP sensor and not the fuel pressure regulator,