Ranger Help

I have a 91 ranger 4cyl (2.3) that I been workin on for my cousin. It starts then dies, starts then dies. but if u feather the gas to keep it runnin till it warms up, it runs great in idel. on the same note it will run fine in idel after its warm BUT, when u give it gas it misses, spits, sputters and tries to die. it also runs like crap under load. I been workin on cars for 20 years and I say M.A.P. sensor but for the life of me i cant find its location, its like it dont have one. Any help or ideas would be great. Thanks