One of the biggest improvements you will get is with the tyres. Are you running R-Spec or better tyres?
On our short tracks, moving from a road tyre to an R-Spec tyre will normally give you around 2 to 3 seconds a lap.
How much time difference is there between your times and the other car's times?
Also, are you comparing apples to apples - what do the other cars weigh and how much power are they putting out.
At a long track, with very long straights, my 968 was around 18 seconds a lap slower than a 911 GT3 RSR, so it is all relative. It was quicker however thna most Cayman S and quicker than all Boxsters. It was also quicker than a lot of GT3's - even though I give away around 200hp.
Cars are subjective, as per my last post - I do not delude myself that I could get into a 911 and drive one quickly - the driving style would simply be too different and I would have to learn how to drive one. Whilst most instructors are quick regardless of car - it still takes time to learn the car itself to be very quick in it.
Another example of relative times. A car magazine ran Audi R8's around Lakeside over here (in road spec). My 968 was 1.5 sec a lap quicker than the V8 and around the same time as the V10. Not sure how hard they were trying, but this is a car that costs around 10x what a 968 does.
I also look at the times that run around Wakefield Park in NSW. I managed a low 1:09 (there is a clip on Youtube - 968 vs GT3). The GT3 smokes me on the straight, but I catch him in the braking zone for the first corner and then get held up everywhere.
Do not under-estimate suspension set-up. Having a car that stays flat and planted will not only allow you to carry more speed, but to also accelerate earlier. The bigger brakes also allow you to carry speed longer prior to braking. All of these little things add up to a big improvement in lap times.
As per previous posts, regardless of the car you have, you will have to tinker with it to get the best out of it. Depending on track, this could be as simply as pressures and alignment/camber, etc, through to major changes to the car. Once the bug bites, it bites hard. But tinkering and looking for the next opportunity to go faster is part of the challenge.
It was even enough of a challenge for me to now start looking at the driver and trying to reduce the weight that this add to the vehicle (which in my case is considerable).
There is no silver bullet here - ever car will have its own unique challenges and issues.
I have seen EVO's throw rods and have a smelly mess on the ground as well. But on most tracks I would be faster than an EVO (not sure about a massive HP version - but a stocker or slightly modified one I would be quicker).
Last time the car was dyno'd it was making 186hp at the wheels - so my car is now power house as well.
You should be able to see lap times from events at the Queensland Porsche Club website for comparisons.
What is interesting as well is that there was another 968 that was stripped and had a cage in it competing in previous years. We used to run in different classes (as his car was some 200kg lighter than mine), but I could normaly just pip him for lap times. To this day not sure what the reason was (18' rims and wider tyres on my car, wheel spacers, etc, etc). But there are differences even between the same car and driver.
I am going to do a Driver Ed day to see just how much lap time is left and whether or not I am going as fast as possible - but until a real race driver has a punt, I am assuming that there has to be a couple of tenths left somewhere.
Another thing in favour of the 968 - we share our ideas freely.