Enigne Issues

I have a 02 Kawasaki ZX-7R.  I lived overseas and shipped my bike back to the states recently.  I followed the owners manual guidance for long term storage.  I had to drain the tank and the manual said to put in 250ml of motor oil in the tank and drain the excess.  I did exactly as read.  I got the bike and filled the tank.  I got the bike recently and filled the empty tank with gas and drove.  I now have an issue with power below 5000 rpm.  The engine stutters and will actually die from a start unless I rev it high and let the clutch out.  I drained the original tank of gas and put in a little new gas and shook the tank to get any oil residue out.  Changed the plugs and drained the fuel system.  Plugs were really fouled.  Bike ran ok, but it started doing it again.  Does anyone think it is the oil or can you tell me what else it might be.  I am leaning on getting a new fuel filter since the oil or bad gas may have clogged it.  If it is the oil, how do I get it out?  Would gas treatments and burning through a couple tanks of gas eventually run out the oil?  Please Help  

One more thing, It was really hot the other day and the bike really started to run like crap.  I think the heat is making any oil residue run to the bottom of the tank.  The next morning I could not even start it.  I had to take the tank off, drain the carbs, and drain off a little gas from the bottom of the tank.  Put it all together and it started up?  Could a weak batter also cause this issue?