sputters on load

[Jock Hiltz]

I have an 1989 W100 with a 318.... it idles fine runs fine when just taking it easy but when I accelerate fast or have to take off on a hill or anything that puts any load on the engine it sputters like it is miss firing. Suggestions?

Asked a mechanic friend and he asked if it had a Mass Air Flow sensor.... im not sure if it has a MAF but there seems to be a unit on the air intake system before the filter that seems to control a flap that restricts the air flow... is that the MAF or equivalent with different name? could that be suspect?

thanks