Poor acceleration, delayed shifting

2002 Santa Fe 2.4 2WD 81,000 mi. Poor acceleration appeared almost overnight, accompanied by a change in exhaust system tone. Transmission is reluctant to shift, especially under hard acceleration. Especially poor engine performance going uphill. Also can hear preignition "ticks". Had exhaust system checked, no leaks. Had engine analyzed, no codes. Two mechanics gave me three possibilities: MAF sensor, incorrect transmission fluid, or a real transmission malfunction. Hyundai wants $95.00 just to put it on analyzer, and I don't trust them because they skunked me on the horsepower class action settlement. How can I tell if it's a sensor (not warranteed) or the trans itself? Can wrong trans fluid cause this? Can MAF sensor go bad without revealing any diagnostic codes? Am I asking too many questions? Please help. Thanks.