ok I will try to explain it so that you guys will under stand what I am tring to say. I have a 98 GSX here is a list of the mods thus far> k&n injen hard pipe to turbo, greddy hard pipe to throtle body,greddy type s bov, mbc turbo xs, up graded pluges and wires, upgraded clutch and fly as well. Ok last weekend me and a friend spent some time putting in a new pacesetter header and a ported t28 and ported o2 housing the porting is only a mild job nothing to radical.also keep in mind that I have the stock exhaust and the stock fuel system too. I keep the boost at 13 to 14 psi thats all I don't want to get denation befor I get the fuel sys upgreaded.
Well as I was saying we put the header and the turbo on and did it right. so I feel, we primed the turbo with oil and spun it once as we pumped the oil in for the start up. the thing was a bit of a head ach to install nothing is lining up with the pacesetter header. With some effort we get it all to line up ok and made sure of no leaks and to my suprize there wern't any no oil no coolent or exhaust I was so glad. Well it was late and I just drove the car home with no boost on. It was after 50 miles of driving that decided to retorque everything when the engine was warmed up a bit. Still no leaks cool, now I decided I would turn up the boost to about 10 psi that should be safe. So I did and the car is really slow no power at all none. so I tried 14. still the car has no power less than I had beforwith the T 25. I thought ok I will try the 10 lbs again and check all my clamps to make sure no leaks still no leaks I could find .
ok now I am getting frusterated I am also getting bad bost spikes after shifts and it seems the more I turn up the boost I am only able to hold about 12 lbs I can hear the turbo spooling and it sounds great a little diff from the t25 I had. Also if I eas in to the throtle to wot in 4th of 5th I can hold way more than 12 psi like 18 and thats not good but in 1 2 3 gears I cant hold more than 12 and it is slow at reving up from 3500 to 6500 rps. hell the 25 was hands down way faster in the car wtf. Am I just over looking somthing did I get it in the car wrong I tried to spinn the turbo and it spun great and it has no wabble why is it that a handa with no mods could beat me so bad in a race right no it aint funny. Is there anyone who might have a idea whats going on with this car of mine ohh ps the turbo was a brand new one not a hand me down . Alos i am not hitting fuel cut i do know what that it i am not pushing enough air by the mass to hit fuel cut . Please help

This seems like an interesting problem. Are you still relying on the ECU for for total fuel/timing management? I would anticipate that you are with a T28. Also, is your boost gauge connected at a manifold source and was it installed before the T28 swap? Just trying to narrow down some things... I am suprised that you are showing boost with the symptoms that you have.

double check that you have the boost controller and wastgate hooked up right. Also make yourself a boost leak checker and look for boost leaks. Check your plugs and gap them.

The stock exhaust is definately not helping you, most likely the reason you're getting boost spikes.

Almost sounds like you're choking on fuel. Do you have a datalogger?

well i had the boost guage on befor the t28 and it is working correctly and i have it connect to the manifold like its sapposed to be. checked the plugs already and there gaped at 28 like there sapposed to be also i rechecked the mbc and it is on right. I am starting to think that the turbo is bad i heard somthing this morning that sounded like a squeel then it was gone after i got to 0 psi and got out of the negative boost. it was only there far a sec. and hasn't came back but that don't mean that its not there anymore

Could the wastgate being opening all the way and sticking open?

As AWD DSM 1 asked, do you have a logger??

I am betting on knock