THings to check plugs, plug leads, coil. And the usual suspect, Air Flow Meter.
You may also be hitting boost cut. Without more info about your car regarding any modifications its a bit hard to say.

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Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i

when im driving along and give some it goes ok to about 4000 then slightly drops out then will keep climbing it keeps repeating like this so im not to sure

VF34 turbo, bigger sti injectors, apexi front mount, autronics sm4 ECU antilag enabled, Greddy air intake, HKS super dragger exhaust, sti 5speed gearbox, exceedy heavy duty single plate cluch, sti cusco front and rear strut braces, sti cusco front and rear sway bars, lowered king srprings on sti shocks
here are some of the mods

this and you still havn't. if you want proper answers give a bit more effort, im sure then no one will give you stupid answers

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98 gf8 Rip

Stop disrespecting Dianella man!

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I'll guess that if you can type a sentence then you can read sentences that others have written?

That said, why are you ignoring what other people have written?

None of us have a crystal ball ffs.......we have no idea what you drive.....Different years have different causes for the problem you have.

What YEAR is your car?

WRX or STI??


So it has bolt on mods....... What fuel pump is in it?

Has it always had the fail spot or has it only just started to occur?

4-5k rpm is peak torque...A weak ignition system will display itself as hesitation in that rpm range.

When were the spark plugs last changed?

Help us help you..........

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[CENTER][SIGPIC][/SIGPIC][/CENTER]
[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]

Won't be air flow meter with AUtronic, you need to check you plugs, leads, and coil. Then put them back if their fine, and take it to a workshop and get them to check your fuel pressure and flow and your crank sensor output waveform.
I've given you some suggestions, you need to take it to a workshop.

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Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i

S-Technic like a Boss.

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2016 Levorg GT-S
Old man spec.

1999 and a wrx to be honest the fuel pump and injectors i didnt do but apparently they can handle it its only running 14psi

fuel pumps don't last forever

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98 gf8 Rip