Several months ago, I did some timed cuts between the Husqvarna 55, Shindaiwa 488, and the Echo CS-510. All three have minor muffler mods, no other mods anyplace.
All three use 18" bars and .325" chains, but the CS-510 was still sporting it's factory POS safety chain, but I ground off all the guards on the links between the cutting teeth.
All three saws are very strong runners, and the tests were conducted several times in the same log. I made 5 cuts with each saw for each test.
The Husquvarna 55 and Echo CS-510 were dead even. The Shindaiwa was 9 seconds behind them on the first test, and 10 seconds behind them on the second test. That's less than 2 seconds difference per cut in a 16" dry Cherry log. Not really much of a difference, and the results could be considered flawed some as all three saws didn't use EXACTLY the same bar and chain.
In any case, the Shindaiwa 488 is a very well built saw, professional quality and features in every area. Not much plastic used on it either. I've got my sights on a 372XP, so the 488 is for sale, as well as a couple other saws to build up the chainsaw fund, PM me if interested?......Cliff