Im having an issue with my 90 Lesabre with 95K miles, under normal driving conditions the engine runs fine, but when i put my foot down to pass it goes up to 3500 rpms and then starts bogging, up until 4000-4500 the engine wont gain anymore Rpms and backfires until the transmission shifts into the next gear, iv be trying to diagnose this problem for a while now have replaced many things in the hope of solving this issue, things i have replaced: MAF,Crankshaft position sensor, Fuel Filter, Coil and Module, Fuel Pressure Regulator, ECM and normal tuneup items (plugs, wires, oil, ect.) it may be a timing issue as i haven't had the time to get the timing cover off and check the integrity of the timing chain, any ideas or solutions are greatly appreciated. Thank You.

Broken or clogged catalytic converter or muffler?????

I had a similar problem with a Volkswagen Passat about a year ago. The car would drive fine during low rpm'*, but when I would try to accelerate at a brisk pace, the engine would rev up to a certain rpm and then it was like the engine hit a brick wall.......wouldn't rev any higher, engine would backfire and had a considerable amount of power loss. The problem turned out to be a broken catalytic converter. $1,200 dollars for a new cat and it was back on the road.......I sold sold the car 5 days later.

the same happened to me so i removed it its currently straight piped to a glasspack, i appreciate the quick response though

however it used to be much worse it would chugg and chuff at 2500 rpms then i replaced the ECM and it solved alot of the issues this is my final barrier untill its a perfectly good running car.

Are you getting any Trouble Codes? Is the Service Engine Soon light coming on and going out as it should, not working at all, or shining your way home?

Also, why were the parts replaced that were replaced? Are you throwing parts at it hoping something sticks or did you suspect something based on info you had?

the only trouble code is for the maf being unplugged it wont run with it plugged in? as far as the parts iv replaced it was under the assumption the engine was running lean under high rpm, and the electronics controlled by the ecm were malfunctioning but they were fixed when the new one was used, and things that needed replaced as they were still 25yr old parts in need of replacement.

i will have to link a video soon to explain a bit better, its a strange issue that i have never experienced before.

did you pull the codes via the check engine light or did you use a scan tool? The Scan tool if it is the more advanced ones can give you info on what your sensors are seeing.

If it won't run with the MAF connected, you probably need a MAF....I know you said you replaced it, but was it a used one or reman? Those reman'* can be bad right out of the box.....