I don't know this particular tuner, but I can tell you what the hi-blend switch is for. It blends the high frequencies in the two cahnnels to reduce noise on weak signals (the reason is a long story....). You sacrifice high freqency stereo separation for less noise.
The IF (Intermediate Frequency) switch may be a bandwidth switch. Is it labeled "narrow" and "wide", or something like that? If it's a bandwidth switch then it's purpose is to provide better selectivity on closely spaced strong signals. The narrow position trades off frequency response for a clear signal. It's good for reducing multipath distortion in urban areas.
The IF (Intermediate Frequency) switch may be a bandwidth switch. Is it labeled "narrow" and "wide", or something like that? If it's a bandwidth switch then it's purpose is to provide better selectivity on closely spaced strong signals. The narrow position trades off frequency response for a clear signal. It's good for reducing multipath distortion in urban areas.