What big old saws are you running? i used to run a Stihl 056S and a Stihl 075.Both very different saws but did the job.
I run both a 088 and 051av that has been pimped out with a custom exhaust system but that only comes out to play once in a while.
I find the older saws have more grunt than the newer ones, my 088 will out proform my 880 any day of the