V40 T4 (1.9) Misfire / backfire - running rich

[Baffler]

I had a cheapo aftermarket MAF turn up today (i wanted proper Volvo, but i just didn't have the funds). ANyways. this seemed to massively improve it, but there was still a slight issue.

With the aftermarket MAF you may experience strange behavour such as the cooling fans running on after switching off the engine. The genuine Volvo MAF sensor is manufactured by Siemens.

Except when i give her more than 50-60% throttle on occasion she really hesitates, and maybe a slight misfire but not sure on that one.

Depending on the mileage this could be a sign of a tired fuel pump. 100k miles is the average life span of the pump. As the T4 can quickly go through a tankful of juice, owners tend to run them low, hence the reason for a tired pump. Do a search in this section of the forum for same.

Another cause of misfire can be the spring, inside the insulator of the coils packs, not making proper contact with the top of the plug. Extend them slightly to rule out that problem.

It does have some cheap induction kit on it, but i did not fit this, it came with the car. The car basically 3 days old to me and a nightmare already .. why didn't it play up on the test drive so i coulda walked away lol

Don't feel disheartened. Once you have ironed out all the little glitches it should be a fine car for many years to come. Try to use, as much as possible, genuine Volvo parts on the T4.

Is the airbox on the turbo uprated or can i use one from one of the N/A models?

I would imagine they are quite similar. I'll check and get back to you on that one...

It also seems to be running a bit better on Texaco 95 ron fuel, i was running it on optimax since i bought it. Could this have any bearing on the remainder of the problem?

Really? The T4 is designed to run on 98 RON so again try to use this where possible. You'll get more MPG plus a little more shove in your nether region