I know there has been much discussion about USB to Serial links not working with Megasquirt etc.
I wanted this facillity as I only had 1 serial out on my laptop and needed to connect both Megasquirt and the wideband lambda controller at the same time.
I bought one of THESE to see if it would work.
Initial tests seem to indicate that the adaptor and drivers work fine with both Megasquirt and lambda controller

Toshiba laptop
MS II V3 MT 2.25
WinXP sp1

Cable supplier NTDWM

FYI the problem with these converters for a couple of years was that the drivers on the CD were incorrect, the device would install but just wouldn't work.

If you downloaded the proper drivers from www.Prolific.com.tw then all was OK.

There are only 3 manufacturers of this USB-Serial chip, Texas Instruments, Cygnal (now Silicon Labs) and Prolific. I've used all three in the past for either integration into products, or just as a cable, all work perfectly.