If you think it is an engine issue, how long since a tune-up? Any applicable trouble codes? You should be able to check mil codes, yourself. You turn key just till the dash lites come on, no further. Cycle the key on--off, on--off, on. Then the mil on the dash starts flashing, you count the flashes to get the codes. Your looking for two digit codes. Check the tps and map sensor. Check for vacuum leaks. Vacuum leaks aren't as noticeable at higher rpms.

This might be a tranny issue?