The VERY FIRST question I posted here, on the day I joined this site was:
"Pesk Carb on 2.5?"
I was upgrading from the .15 and heard all kinds of bad things about keeping that engine in tune.
Some time later, I bought an ACNCM cooling head through the For Sale forum here, and all the tuning issues were gone. Not a carb problem, but a stock head that was unable to keep the engine temp consistant.
I tune LOTS of engines at the local track, 90% being stubborn 2.5s.
Any time anyone has a problem with one I tell them I'll get it running for that day, but I won't do it again till they get a better head.
It's not the most powerful engine, or the highest revving, but with a good head, it's totally reliable and dependable.