Sipah e Sihaba was founded in 1985 purportedly under the auspices of military command. They were quite active in Jhang during Gen Zia's time. In 1996 they split and formed Lashkar e Jhangvi which was even more violent.In my observation, Sipah Sahab emerged after death of Zia ul Haque.
It was mess of 90's, at that time RAW and IRGC were hosted well in Pakistan by PPP.
During Zia rule, Pakistan's medical colleges and Engineering universities, were full of Iranian students.
Majority of Irani students in Pakistan during the 80s had actually run away from the mullah regime and did not want to be conscripted to fight Iraq during the Iran-Iraq war. In my alma mater NED there were students who were still enrolled after 10+ years for a 4 year course because they did not want to go back. Singer Mohammad Ali Shehki was a prime example of that.