\documentclass{book}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage[gen]{eurosym}
\usepackage{textcomp}
\usepackage{graphicx}
\usepackage{etoolbox}
\usepackage{titleps}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{float}
% use hidelinks to remove boxes around links to be similar to Texinfo TeX
\usepackage[hidelinks]{hyperref}

\makeatletter
\newcommand{\Texinfosettitle}{No Title}%
\newcommand{\Texinfotheinclude}{}%

% redefine the \mainmatter command such that it does not clear page
% as if in double page
\renewcommand\mainmatter{\clearpage\@mainmattertrue\pagenumbering{arabic}}
\newenvironment{Texinfopreformatted}{%
  \par\GNUTobeylines\obeyspaces\frenchspacing\parskip=\z@\parindent=\z@}{}
{\catcode`\^^M=13 \gdef\GNUTobeylines{\catcode`\^^M=13 \def^^M{\null\par}}}
\newenvironment{Texinfoindented}{\begin{list}{}{}\item\relax}{\end{list}}

% used for substitutions in commands
\newcommand{\Texinfoplaceholder}[1]{}

\newpagestyle{single}{\sethead[\chaptername{} \thechapter{} \chaptertitle{}][][\thepage]
                              {\chaptername{} \thechapter{} \chaptertitle{}}{}{\thepage}}

% allow line breaking at underscore
\let\Texinfounderscore\_
\renewcommand{\_}{\Texinfounderscore\discretionary{}{}{}}
\renewcommand{\includegraphics}[1]{\fbox{FIG \detokenize{#1}}}

\makeatother
% set default for @setchapternewpage
\makeatletter
\patchcmd{\chapter}{\if@openright\cleardoublepage\else\clearpage\fi}{\Texinfoplaceholder{setchapternewpage placeholder}\clearpage}{}{}
\makeatother
\pagestyle{single}%

\newpagestyle{custom}{%
\sethead[\thepage{} \sectiontitle{}][\thesection{} Section \thesection{} \sectiontitle{}][\chaptertitle{} \thechapter{}]%
{}{}{}%
}%
\pagestyle{custom}%
\renewpagestyle{custom}{%
\sethead[\thepage{} \sectiontitle{}][\thesection{} Section \thesection{} \sectiontitle{}][\chaptertitle{} \thechapter{}]%
{}{}{}%
\setfoot[\chaptername{} \thechapter{} \chaptertitle{} \Texinfosettitle{}][\Texinfotheinclude{}][\texttt{\chaptertitle{}}]%
{}{}{}%
}%
\pagestyle{custom}%

\begin{document}
\label{anchor:Top}%
\chapter{{ch--ap}}
\label{anchor:chapter}%

\newpage{}%
\phantom{blabla}%

after ch--ap first page

\newpage{}%
\phantom{blabla}%

after ch--ap second page

\section{{sec1}}

\chapter{{chap 2}}

\renewpagestyle{custom}{%
\sethead[toto][titi][]%
{toto}{titi}{}%
\setfoot[\chaptername{} \thechapter{} \chaptertitle{} \Texinfosettitle{}][\Texinfotheinclude{}][\texttt{\chaptertitle{}}]%
{}{}{}%
}%
\pagestyle{custom}%

\newpage{}%
\phantom{blabla}%

after everyheading before chap 3 first page

\newpage{}%
\phantom{blabla}%

after everyheading before chap 3 second page

\chapter{{chap 3}}

\newpage{}%
\phantom{blabla}%

\renewpagestyle{custom}{%
\sethead[toto][titi][]%
{toto}{titi}{}%
\setfoot[aa][bb][cc  dd]%
{aa}{bb}{cc  dd}%
}%
\pagestyle{custom}%

\end{document}
