You might have seen my last message, but now i was wondering what is better a whole new muffler system or just the muffler tip. What im looking to do is just gain some of my lost Horsepower, to maybe cover the A/C and gain alot more when the A/C is not running.

I know that muffler system are alot more expensive and harder to install, but what would be better for gaining the lost HP.
I have a 1999 A6 2.8 its a very nice car like all Audis....

 

Muffler tips don't increase horse power, they are for looks and changing the exhaust sound alone.

Exhaust system will potentially change horse power, but this is generally seen as an expensive way to gain a few horses, and doing it properly means changing it from the manifold to the tailpipe. Even then, only expect maybe 15 horses on average car. So, on an average car, you spend 2-3K to gain 15HP... Only worth it when you already did the easy stuff and are really entering the upper echelon of performance tuning. Again, to be clear, I have no idea how much HP changing the exhaust on a 2.8 will give you, I am giving 'general' numbers here.

AC will take about 5-6 HP when its running full out. Want the power back, SHUT IT OFF. If you are racing or something, (no sure why you would in a 2.8) turn it off, the rest of the time, who really cares about the 5-6 ponies? If I remeber corectly, Audi cuts off the AC for 2-3 seconds when you kick it down anyway. (My old 5000 turbo did anyway.)

The fact is this, and not being mean, just factual: The 2.8 is not a fast car, it will not be, it will cost alot to try and make it be. Its a nice car, but if you are really trying to make it fast, I would recommend trading it for a 2.7. Trust me, you will save alot of money in the long run and have way way more performance out of a rechipped 2.7T.