problem with Pro-M positions !!!!!!

[HAITHAM]

I have Pro-M 80mm.
When I mount it in vertical position car bucks & pop sound in the exhaust when left the acceleration paddle in 4th gear at high rpm, but the performance is up.
keeping it inside the engine compartment it will cure all problems, but the performance if off.
What is the solution ?

------------------
Black 94 COBRA # 926/5009
TFS track heat heads (ported), Cobra intake (ported), 24# Injectors, 3/8" Phenolic spacer, E303 Cam, TFS 1.7 rr, BBK 1 5/8" headers, BBK 65mm TB, Pro-M 80mm, PIH kit, FMS 3.55 ratio, BBK 190 lph fuel pump, Paxton fpr, MSD'S, March Pulley's, Pro-5 tower power shifter, Autometer shift light (5600), Intellitronix Air/Fuel gauge, Eibach Sportline Springs, Tokico 5-way adjustable, Edelbrock Mufflers w\ 2.5" exhaust system, Clear Marker Lights, Aluminum Grill, Pfgoodrich