Is there a specific diet I should choose to improve male erections?

There are no diets which will improve either the quality or frequency of erections. In the past people have talked about "aphrodisiacs" which are suposed to improve your ability to have sex. Some of these so called aphrodisiacs were things like oysters (assumed to improve your virility simply because they have a similar taste to semen) and aspargus spears (because some people thought that its shape resembled an erect penis). There is no scientific evidence that any food will have any effect what-so-ever on your abilty to have erections. If you have any problems with this aspect of your life see a doctor.