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Anyone Have An 07-09 Gt500 With Offroad Jlt Big Air And Vmp 2.5 Pulley?

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Recently added a VMP 2.5" pulley with 90mm idler to my existing mods:


* JLT Carbon Fiber BIG AIR intake (127mm)

* Offroad X (catless) free flowing exhaust

* NGK TR6 gapped to .032


I'm running a 93 Lund Tune that should already be tuned for increased air from the 2.5" pulley (per Lund).


My boost went from about 7 pounds to 10-11 pounds. Car pulls fairly well but stumbles on startup and for the first 4-5 minutes of operation.

Is this normal? I was expecting to be in the 13-14psi range with these mods?

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I'm starting to wonder if the stock belt is actually slipping.

Anyone that's done these mods please chime with your OEM boost gauge readings and whether or not you've experienced belt slip with the 2.5" and 90mm idler?

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