420A Dyno Graphs/loss of power

[1996Eclipse420a]

This dyno graph is for an example. My 420a turbo hits peak boost, then drops off power much like this graph. What could be causing this issue, and does anyone else with a stock head, have any dyno graphs to post for comparison. Boost peaks at 4750rpm, then falls off a good 30-40hp. On 18psi car made 274hp 300tq.

PTE 5431, FIC 775cc injectors, hallman MBC, aeromotive AFPR, NGR BOV, Tial 38mm WG, wallbro 255 fuel pump. Built bottom end and stock head. Tuning with AEM FIC 1913.

Could the eBay intercooler be causing a loss of power like that? If so I'll buy a name brand one. Possible valve float? Car doesn't sound out of the ordinary. What could be causing the chart to read like this? From my understanding a dyno graph shouldn't look like this. Boost leak test has already been done and no leaks were found. I have a video I could upload as well if needed.

 

[Slo2gen]

Are you running the factory ignition map?

 

[bmxfelon420]

Looks pretty normal to me. Those stock 420 heads have tiny ports.

 

[jared98gst]

.48 hot side?

 

[1996Eclipse420a]

.48 hot side?

.63 hot side.

 

[1996Eclipse420a]

.48 hot side?

That's not normal. Here is an actual graph of mine on 16 psi before the tuning began. Power drop off is still the same I might add

 

[1996Eclipse420a]

Are you running the factory ignition map?

I'm running 12psi stock timing then I take -1 degree from 13-18psi.

 

[1996Eclipse420a]

Here is the graph.