new turbo questions

[smokeisfun]

well, i got my new (used) turbo from benn on here...its off a 3rd gen and i put it on my 98 12v....anyway...i love it...but there is one thing...it seems that if i lock my t/c and am in 4th gear at say 45mph...and i mash the throttle...boost will slowely come up...like it should...but then at say 1500rpm im at 30psi and then it starts to bark but then it will come on up to 40-45 psi...im not sure if this is the right terminology, but it seems like its surging/stalling....but you guys tell me what you think it is...

thanks