My Sv6 is has started running very rough!

[StrackerZ]

Hey guys new to the commodore forums, but always refer to them when im in need.
Recently a bought myself a 05 vz Sv6 with 110,00 on the clock. As i P plater i was very keen to make some mods as to suit my self satisfaction.
I got my Stereo installed first which consists of 8 speakers, Xplod h/u, 2 Amps and 2 subs. not long after i manged to save some more cash and get the Exhaust done as to a mates suggestion.
A 2.5 inch system from cats back, and an Aloyetec SS cool air induction Growler kit installed also.
About 6 weeks after i had the induction kit installed i noticed that whenever i gave her a bit of stick, at about 5000rpm the acceleration became very "Chuggy" and rough, until the shift.
Then just this week it has started happening through every gear at any random moment during the RPM raise. at any point if i want to push hard into a lane, or merge with a bit of authority my car hasnt got it in it to produce. Also while idling the car is chugging alot, as if it is really struggling and feels as though it is about to die.
And now today ive noticed when i tried to see what happens at low speed to give it heaps, the exhaust was like shooting out like a spluttering sound. I have lost a ridiculous amount of performance and acceleration and i just want it fixed.
It's absolutely devastating atm, cause my old vt had more problems then u could name and im feeling completely out of luck. Please if anyone has any suggestions let me know.!!!! thank you very much.
Also if anyone lives in the Narre Warren region and knows there way around cars let me know if you around, n i could possibly demonstrate to you whats going on.

[trenooo]

vcm tune, under 1 g, will see big improvemens from the mods made

[Luke52]

110,000 on the clock?

Spark plugs will be due very shortly, no harm in changing them 10,000km early. I'd change them first.

[torana355]

If the growler uses an oiled air filter it may have dirtied the AFM which can cause issues.

[treyflip]

Clean your maf with maf cleaner first! Then check your coil packs one by one and then change plugs.

[fjwb]

I recently looked at an SV6 with 70k on the clock. the owner was complaining of a lack of power. These are meant to have longlife plugs and last upwards of 100,000km. Luckily I pulled the plugs out of curiosity and found they were absolutely stuffed and it did not have the correct plugs. I verified the part number with my connections at Holden, and found that the plugs fitted were superseded on a date prior to the build date of the car. So somehow the car was factory fitted with the wrong plugs.
A new set of plugs and the owner couldn't believe the difference.