OBDII boost gauge
 

I'd like to how if boost gauges that takes readings from the OBDII is accurate enough? Or is it better to use sensor (the type that has nylon tube to a control box which then sends signal to the gauge) or even mechanical type gauges?

I think its mainly just a matter of opinion. OBDII will be accurate, but there will be some lag depending on how you execute it. Electric boost gauges are good, and so are mechanical.

I installed a mechanical boost gauge on my last car and had no issues with it, so I could be a bit biased.

The OBD2 gauges (I have a p3cars one myself) display what the ECU knows, it'll be dead on albeit with a tiny amount of lag. Idk about the stock MAP sensor but any properly scaled Omni is just as good if than the standalone senders. Seeing as how MAP is used in speed density it better be accurate :p

It'd be similar lag to an electronic needle gauge with a stepper motor. Mechanicals are the fastest but they can lose accuracy over time. The lag is such a small amount that unless you have a mechanical and digital next to each other you can't tell.

Ok thanks guys. Yeah I'll be upgrading to an Omni 3 bar map sensor for my FI tune.

The p3cars gauge is what I'm looking at getting....

I got one if you want it, be back in Perth tomorrow too.

For boost, if the MAP sensor is scaled the readings are correct.

However, for AFR you should use an external sensor (Innovate, AEM, etc.) wired to the analog signal wires on the p3 gauge. The factory air/fuel sensor is not totally accurate.