Afraid you can't do anything for that.
I've never really understood why people say this...
Wide grip benches (incline, flat, or decline) pump the chest in totality and create a noticeable widening effect at the shoulder insertion points. But they don't give the inner chest much of a pump for most people.
To accentuate the inner cut between your pecs, you need to be doing an exercise that creates maximum contraction of the entire pec. Just like concentration curls provide biceps with peaks for those that are genetically predisposed to have them.
I would suggest that you try doing close grip flat or incline free bar bench presses (hands 6" apart). Do these AFTER your heavy wide grip sets so that the muscle is already relatively pumped before you start. Once you get used to balancing the bar with your hands this close, work up to using about 60%-70% of your max repitition weight.
You don't need to bring the bar all the way down to touch your chest since anything below about 6" above your chest is only working your triceps, which isn't the goal of this movement. Also, don't forget to REALLY contract your chest muscles and fully extend your arms at the peak of the movement to get the full effect of this exercise.
A secondary benefit is that these also work your triceps, so they help in the overall development necessary to keep your benching maximum climbing.
Karma?