Please help with the design: 22 parameters influencing single outcome

I would appreciate your advice on statistical design.

There are four subjects, each was tested with 171 stimuli. Each
stimulus is described by 22 parameters. A test yields a single
numerical outcome. I am interested whether the parameters of stimuli
influenced test results.

One idea is to average the subjects' test results for each stimulus
and calculate partial correlation coefficients between the average
test result and the 22 parameters.  However, this approach offers no
view into the intersubject variability.

Another idea is to categorize the stimuli according to each
parameter's value: e.g. >=median vs. <median.  Then I would check
whether test results obtained with stimuli which have high (>=median)
parameter values differ from test results obtained with stimuli which
have low (<median) values.

I was thinking of a 23-factor ANOVA, with one repeated mesures factor
(subject) and 22 factors=parameters.  In the design, only main factors
and interactions (subject x a_parameter) would be analyzed.

In such way, I would get a measure of whether any of the parameters
influences the test result (high Fs for 22 factors-parameters) and a
measure of across-subjets consistency of this influence (low Fs for
subject x parameter).

I would like to see your comments.