Hell of Problem!! Advise required

I own a 1985 Model Subaru. It has a 4efe engine. Since its convert no one with computer touches it.. Say... wrigin kharab hai .. blah blah blah.. Now the problem Part...

I used to have a great pickup when I bought the engine.. but soon i had to overhaul it. Now ... engine hesitates to accelerate.. I took to many Mechanics.. in Mithu khan ka Aihata.. but they all lack one thing... BRAINS.... I finally fixed the gas problem myself by advancing the distributor and then the car started to pick comparitively better than before but its acceleration was still less than that of a Mehran. On petrol a lot of piston knocking occured... Now... suddenly... car has started misfiring on Petrol... works fine on gas.... but on petrol engine hesitates to accelerate.... and misfires a lot.. Only way to move the car from halt is to increase the RPM to around 4 - 5 and then slowly release the clutch.. It misfires a lot on Low RPM..

Another way to drive on petrol is to just slightly push the accelerator .. when it will misfire it release it and then suddenly push the accelerator.. if don`t correctly the car keeps on moving ... which is very hard to get along with.. Esp.. if u get stuck on a slope.. very very hard to drive the car...

I check the fuel pump... it works fine.. NOW what else can I Do.. anyone please advise me how to CHECK my MAF sensor and Throttle position sensor.. I think they are malfunctioning... Please advice.. I want to fix it myself rather than to take my car to these so called Mechanics...