Gul dispelled fears that the Pakistan attack would crumble without strike bowlers Shoaib Akhtar and Mohammed Asif as he claimed 5-65 and was ably supported by Nazir with 3-42.
Only West Indies captain Brian Lara was able to offer resistance with his stubborn 61.
Pakistan finished the day on 39-1 when bad light stopped play with 18.1 overs still to be bowled.
Batsman Younis Khan reached the 1,000 runs milestone in one calendar year when he reached two, he remains on 10 not out.
Gul took four wickets for just 11 runs in his third spell after lunch, including the prize scalp of Lara.
Umar Gul: What bowling crisis?
The West Indian captain hit Gul to the boundary to reach his 48th Test half century, his first in five Tests in Pakistan, but the bowler had his revenge when he produced an unplayable in-swinger which took an took an edge and flew to wicket keeper Akmal for a regulation catch.
West Indian batsmen Dwayne Bravo and Dave Mohammed, gave their captain some support with 32 and 35 runs respectively.
Once he had Lara, Gul ripped through the tail for his third five-wicket haul in his 12th Test, and also reached his 50th wicket in Test cricket.
The first session belonged to the home team who bowled well with Nazir leading the way.
The West Indies started positively befire Gul got his first wicket, that of opener Daren Ganga for three.
Nazir then took three wickets off 12 deliveries to rock the tourists, trapping Chris Gayle leg-before for 34, Ramnaresh Sarwan (three) caught in the slip and Shivnarine Chanderpaul (five) leg-before to leave West Indies reeling at 52-4.
Gayle hit six boundaries in his rapid 34.
Bravo, who hit a brilliant 108 in his team's tour opener earlier this week, holed out to leg-spinner Danish Kaneria for 32 while Denesh Ramdin (12) miscued a sweep off Kaneria's last ball before lunch to leave West Indies 122-6.