I think what we are seeing here is something that was matter of fact 20 years ago but in these days of plug and play still leaves people baffled. All engines are different. sometimes very different. Its not unusual for a factory fresh engines to differ as much as 10% in power out put. Manufacturers spend a small fortune developing generic parts that are a compromise that allow for variation in stock engine output, the map is a great example. The map has to work at high and low altitude with different air pressures, with poor fuel or in 40c temps or in -20 as well. On top of that it has to allow the engine to pass emition tests and return the absolute best MPG it can at the same time. Air filters have to flow air in a mountain valley in Switzerland or in a sand storm in Saudi and so on. Each part rely s on the varying info or correct operation of the other parts around it in any conditions and that is the compromise the tuners try to over come to get more from the engine. Its fine tuning for the prevailing conditions.
The idea that small after market tuning houses can then produce generic parts at a fraction of the cost of original parts that simply bolt on and do a better job needs to be qualified because these parts remit is much tighter and therefore need to be matched to the individual engines in order to do their job as their flexibility has been "tuned out" in order to make them more efficient and thus do their job better..
Is this teaching people to suck eggs ? or even making sense
The plug and play comparison is quite good i think. You can buy an upgrade for your computer, say a new DVD drive. You install it and it works under the generic map but to get the best you need to fine tune it with a new driver. You can get several more upgrades and they work the same. Then you buy a new operating system and suddenly all you up grades need new drivers. All the parts need to fine tuned to each other again to work better than the generic plug and play of the mother board will allow.
The car is the same and while after market manufacturers like to keep the idea that their products will simply bolt on and do a better job than the original at a fraction of the cost, the truth is you may be lucky but chances are you may not. Rolling roads are not installed at tens of thousands of pounds for the local nova boys to have Saturday morning shoot outs, they are essential to record how, many different add ons are interacting with each other. Back pressures from after-market exhaust working against increased airflow from CAI's and Increased boost placing heavier loads across plugs, burn time in cylinders altered by different advance curves on ignition and a hundred other parameters that need to match in order to get optimum performance from each part.
To make matters worse people then pick and choose what parts to change rather than sticking to a tried and tested route. So one guy has a cat back non res and the next has a full decat res system..the next has a large bore down pipe as well and all three expect their parts to work out the box and give huge improvements.
My advice to anyone who wants to go tuning is speak to an expert who really knows their stuff. Follow a well trodden route if finance is not unlimited. Make sure each part has its "driver" installed but dont then forget about it. Reckon on the next part effecting the first part and resetting that again as well and so on. eventually get the whole package set up on a dyno and as S3alex says get data logs for the engine so you can see exactly how each part is interacting with the next.
Performance parts are made to have much finer parameters to work under. They get performance by focusing their operation/efficiency and thus they do not have the flexibility of generic parts hence the need to fine tune each part to its job.
As someone who is older and is old school when it comes to engine tuning it makes me a little cross that manufacturers sell these parts as "bolt on power" and even give forecasts of exactly how much you will gain !! which is nonsense in its self !! It also anoyes me how many people there are like Cheese who are left to work it all out by themselves because the after market manufacturers forgot to mention that their parts would need to be professionally set up, maybe many times as more and more parts are added.
I.m going to shut up now because I doubt anyone will read or believe this and i'm going back to bed.