ca18det gt28r turbo help

[Frunzman]

Ok, first off im new to this site. i recently purchased a 1992 240sx HB. it has a ca18det out of a 90 with a gt28r turbo, turbox's bov so on and so forth. the car is tuned at 15psi. i have a safcII but no wideband at the moment. not knowing too much about the safcII, i accidently switched from RPMS to KMKS and wanted to switch it back, changed a few things on accident but got them back to normal. at least i thought. took my car out last night, and on the highway i notice its only boosting at 6psi. surging pretty bad, i hit the gas, boosts to about 7-8, then drops right back down to 6. really weird. so i took the car right back home. still doing the same thing, surging hard in 2nd 3rd then not so bad in higher gears. mostly mid range surge. my boost controller is VERY sensitive. i actually just had a piece of tape on to hold it in place, but being its cold i noticed it fell off and was very close to my alternator belt so i thought possibly it hit the belt and twisted, turned one notch and drove it, running at 7 psi. turned another notch, 8 psi. i thought problem solved, turned 4 notchs and it only went to 9, turned another 2 notches and still at 9. seems to boost fine, no more surge, i even thought my iac valve was bad because i was getting a weird idle, when i turned boost up that went away as well. im afraid to turn the boost any higher just in case theres something else wrong. listened for a boost leak heard nothing, checked vacuum lines and intercooler piping all tight. first stop on my list is probably switch out the boost controller with a friends to see if that is malfunctioning, does ANYONE have an idea of what this could possibly be? im at a loss its confusing the hell out of me. any help is much appreciated. thanks in advance.