First a little Automotive Repair 101. There is no such thing as a mechanic in a can. if you want a fuel-injected engine to run poorly, all you have to do is keep adding chemicals to the fuel tank. Most "fuel line antifreeze" and "fuel conditioner" contains large amounts of methanol. Most automotive engines (except flex-fuel engines) cannot handle much more than 10% methanol which is already in the fuel when you get it out of the pump. The problem with most of this stuff is that if you add this stuff to your fuel tank, the methanol level can sky-rocket (depending on how much fuel is in your tank) and can actually cause the engine to run so bad as to cause a no-start condition. I have had to drain and clean out fuel tanks because of people putting that stuff in there.
If there is water or contamination in your fuel system, the fuel tank needs to be drained out and have fresh fuel added. "Miracle Cures" from a bottle or can will usually cause more problems than they fix. There are those that will disagree with this statement and will try to defend their favorite brand of "chemical technician", but all I have to say is that I am speaking from 36+ years of experience and having to clean up the messes many times...keep your comments.
OK, Enough preaching...Your problem may very well be caused by problems in the fuel system. The correct way to diagnose it would be to check your fuel pressure. The fuel pressure needs to be high enough to meet the specifications for your vehicle [38.4-44.0 psi (2.7-3.1 kg/cm 2 )] and should hold this pressure when the engine is turned off. If it is not high enough or if it does not hold pressure properly, it could cause the symptoms that you are describing.
Please also review this article:
What Else Could Be Wrong?