Can’t for the life of me figure out what the issue is.

09 MCS. Car is extremely slow after 4500rpm. I can only get to about 5-6psi while under 4500rpm and the boost builds slow. The boost drops to next to nothing (0.5-1.5 psi) after 4500ish rpm.

No check engine codes except for my secondary o2

I’ve double checked the vacuum lines. The wastegate has some play but doesn’t seem out of the norm compared to others (based on videos I’ve seen online). DV has no tears. Boost converter has vacuum lines still connected (I don’t get any weird kazoo noises when I turn off the motor). Inspected the turbo, there is no shaft play and it the turbine spins and doesn’t leak oil.

Mods: intake, catless dp, exhaust, intercooler, gfb+ dv

Only thing I can think of is the waste gate (because of the play) but wouldn’t that throw a low boost code?

It very well may be the wastegate. When mine went out, it still worked, but didn’t seal all the way, so it would build some boost, but not quite as much as expected, especially under a light load.... that’s when I would get a CEL, but it took a very specific set of conditions to get the CEL (light load on an incline at hwy speeds). If it’s not a boost leak, you will probably need to pull the downpipe and check how well it’s actually closing.
Mine was diagnosed with live data logging and a borescope, but without one just pull the DP to check the wastegate.
Also check the wastegate actuator to see if It closes the wastegate at around 15 inHg.
keep us posted on how it goes. Good luck.