help 1996 civic 3dr Problem

Iv just recently purchased a 96 civic 3dr from a buddy who had to move and couldnt take the car with him. its been a project car that i rutinely helped him work on. buying it i knew there would be some problems because we both are not professinal machanics. so here in lies my situation. the car has many mods most recently a gredy turbo with e-01 multi display. this was the last upgrade he did to the car i think, and ever since the car has not run right, im posotive he hasnt had it tuned since then so im thinking this may lead to the problem. the problem is in first gear at less than 1000 rpms the car bogs down and sorta goes in to a spastic engine shake and rev-limiter kind of sound starts and wont stop untill the car is either shifted to secound or the rpms drop back to idle, it allso does this in 2 at 1200 rpms 3rd at 2000 rpms and 4th and 5th at about 5000 rpms, the car wont go past 90 mph. One of my friends thinks it could be one of two things, A either the boost coming in is to much and has no where to go due to the stock headers or B the turbo and multi display need to be tuned properly.

Any help or suggestions that can be given would greatly be apreciated and please excuse the bad spelling

Thanks will