hi all, newbie on here, some help and advice please,

the car is a 1990 saff cos 2wd, breif spec, l6 330 chip, 3 bar map sensor, dark greens, std turbo new -34 actuator gpa head gasket,mongoose system, gpa filter,rs500 intercooler

the problem i have is that when car boosts any thing over 10 psi it coughs and splutters like mad, ive changed the plugs checked the rotor arm cap and leads coil ect,

any info would be great thanks