Stroker Motor wont Rev pass 5200Rpm

I have a 402ci stroker motor based on the factory 318ci LA motor. I know this is not a very common stroker but we're Mopar people and were different.

The motor has custom Ross forged Pistons, Forged connecting rods, and a Forged 4-inch stroker crank. The heads are mildly ported 360 heads with Harland Sharp 1.5 roller rockers. I believe the push rods are factory length. I am not sure what cam is in the motor maybe off the shelf Mopar Purple Cam. The MSD box is set to 7k reline and the car also has Fitech Fuel injection which is also set to 7k reline..

The car has a custom turbo set up and set for 9-10lbs of boost. When I take the car out for some spirited driving Ive notice the motor will not rev pass 5200-5300rpm in either 1-2-3 gear. I first maybe it was the spark plugs blowing out under boost but I have changed plus and gapped them tighter and and still having the issue.

Any and all advice will be appreciated.

Jared