This article reviews the decay studies of neutron-deficient nuclei within the mass region \ensuremathA=56--100 performed at the Ion-Guide Isotope Separator On-Line (IGISOL) facility in the University of Jyväskylä over last 25 years. Development from He-jet measurements to on-line mass spectrometry, and eventually to atomic mass measurements and post-trap spectroscopy at IGISOL, has yielded studies of around 100 neutron-deficient nuclei over the years. The studies form a solid foundation to astrophysical rp -process path modelling. The focus is on isomers studied either via spectroscopy or via Penning-trap mass measurements. The review is complemented with recent results on the ground and isomeric states of 90Tc . The excitation energy of the low-spin isomer in 90Tc has been measured as \ensuremathEx=144.1(17) keV with JYFLTRAP double Penning trap and the ground state of 90Tc has been confirmed to be the (8+) state with a half-life of \ensuremathT1/2=49.2(4) s. Finally, the mass-excess results for the spin-gap isomers 53Co m and 95Pd m and implications from the JYFLTRAP mass measurements for the (21+) isomer in 94Ag are discussed.