May one use for Eiruv Tavshilin products that one does not eat due to a stringency?
Some Poskim rule it is invalid to use for the Eiruv any food that one does not eat even due to merely a Chumra. Others conclude that while initially one should refrain from doing so, in a case of need the Eiruv is valid.
May one use machine Matzah, Gebrochts and other non-Pesach products for the Eiruv Tavshilin of Pesach?
This follows the same ruling as above, and hence one should avoid using for the Eiruv Tavshilin products that one is careful not to eat on Pesach. This, however, only applies if the food is also not eaten on Shabbos, such as when Shabbos falls during the Yom Tov of Pesach. However, if Shabbos falls after Pesach [as explained next] and the food will be eaten on Shabbos, then the food may be used.
Shevi’i Shel Pesach that falls on Friday in Eretz Yisrael: So long as the food used for Eiruv Tavshilin can be eaten on Shabbos, it is valid even if on Yom Tov it cannot be eaten. Accordingly, residents of Eretz Yisrael who only keep one day of Yom Tov may use for the Eiruv Tavshilin foods that they avoid eating on Pesach but will eat on Shabbos. Thus, when Shevi’i Shel Pesach falls on Erev Shabbos, residents of Israel may use for the Eiruv Tavshilin machine made Matzah, Gebrochts, and Kitniyus products, which they will eat on Shabbos.
 See Hisorerus Teshuvah 2:31; However, see regarding Eiruv Chatzeiros Michaber 386:8 that it is valid to use foods Teruma even though it is not fit for Yisraeilim and Levi’im; See Kol Bo 59; Orchos Chaim Eiruv Tavshilin 3; Yom Tov Kehilchaso 25 footnote 132; See also Ketzos Hashulchan 105 footnote 20 who implies it is not an issue.
 The reason: As the purpose of the food of the Eiruv is that it considers one to have already begun his Shabbos cooking in which case he may continue and finish off the cooking on Yom Tov. However here, since he will not be eating the food on Shabbos due to his Chumra, this justification is not applicable. [Hisorerus Teshuvah ibid]
 Nitei Gavriel 82:14 in name of Divrei Shalom 4:91
 Nitei Gavriel 13:4 in name of Michla Diesvasa 45; Nitei Gavriel Yom Tov 82:15 in name of Ketzos Hashulchan 105 footnote 20 and Hisorerus Teshuvah ibid [however in truth the Ketzos Hashulchan does not make any mention of this matter, and simply states that one cannot be Mezakeh to others when using such a product, such as machine Matzah, as perhaps other people do not want to be Zoche in such foods over Pesach. However, regarding the person himself, no mention is made in whether he can use it for his Eiruv if he so chooses, even though he is Machmir not to eat it.]
 Tzitz Eliezer 14:54; Yom Tov Kehilchaso 25 footnote 132