Is it true that chances to get your wife pregnant with baby (boy) is High, if having sex directly after ovulation time & following day. Or it's myth..

Gender selection. The medical literature doesn't support that claim. The only procedures to change gender selection are to perform gender selection procedure. See my web site, to learn more.
Slightly increased. Since sperm with X chromosomes survive longer but sperm with Y chromosomes swim faster, it is slightly more likely that a baby will be male if sex is at or just after ovulation and slightly more likely that the baby will be female if sex is a day or two before ovulation. Hope this helps.